Apple Watch vs Fitbit Flex: Why I Switched

I’m replacing my Apple Watch and Fitbit Flex because neither device fully covers what I need from a fitness tracker: the Apple Watch is overkill for daily step counting and battery life, while the Fitbit Flex is too limited for serious workouts and heart-rate data. This article explains the specific reasons behind that decision, compares the two approaches, and helps you decide which type of tracker fits your own habits.

Background: Two Different Philosophies

The Apple Watch and the Fitbit Flex represent two distinct ideas about wearable tech. The Apple Watch is a full smartwatch: it runs apps, takes calls, tracks workouts, measures heart rate, and offers an ECG, fall detection, and crash detection. It’s essentially a small computer on your wrist. The Fitbit Flex, by contrast, is a minimalist band that focuses on steps, sleep, and basic activity reminders. It doesn’t have a screen, a heart-rate sensor, or GPS. The Flex line was discontinued years ago, but many people still own one, and the comparison remains useful because it highlights what each type of device does well and where it falls short.

When you put them side by side, the real question isn’t which is “better” in the abstract—it’s which one matches your priorities. If you want a notification hub and a broad health platform, the Apple Watch wins. If you want a cheap, unobtrusive step counter that you charge once a week, the Flex is hard to beat. But if you want something in between—accurate fitness tracking, long battery life, and a screen that shows useful data—you may find yourself replacing both, as I did.

Battery Life and Charging Hassles

Battery life is often the first reason people switch. The Apple Watch typically needs to be charged every 18 to 36 hours depending on the model and usage. That means you either charge it overnight (and lose sleep tracking) or charge it during the day (and lose activity tracking). The Fitbit Flex, on the other hand, lasts about five days on a single charge, and the original Flex lasted up to seven days. That’s a huge difference in convenience.

For me, the daily charging ritual became the main annoyance. I’d forget to charge it before bed, then have to decide between wearing a dead watch or skipping sleep data. The Flex’s longer battery meant I could wear it continuously for a week, but its lack of a screen meant I had to sync to the app to see anything. Neither was ideal. The middle ground—a tracker with a small display and a five-to-seven-day battery—is why many people end up replacing both.

Fitness Tracking Accuracy

Step counting is the core function of both devices, but they don’t always agree. The Apple Watch uses a combination of accelerometer, gyroscope, and GPS (on models with GPS) to estimate steps and distance. The Fitbit Flex uses a simple accelerometer and a proprietary algorithm. In general, both are accurate for steady walking, but they diverge during activities like pushing a stroller, riding a bike, or doing upper-body exercises.

For example, if you’re pushing a shopping cart, your arms aren’t swinging, so both devices may undercount steps. If you’re doing arm curls, the watch may count extra steps because it senses arm motion. The Apple Watch tends to be more accurate for running because it can use GPS to calibrate stride length, while the Flex relies on a fixed estimate. For heart rate, the Apple Watch has an optical sensor on the back; the Flex has none, so it cannot track heart rate at all. If you care about cardio zones, the Flex is simply not enough.

Sleep Tracking and Wearability

Sleep tracking is another area where the two devices differ sharply. The Fitbit Flex was one of the first consumer devices to offer automatic sleep stage estimation (light, deep, REM) based on movement and heart-rate variability—though the original Flex didn’t have a heart-rate sensor, so it only estimated sleep vs. wake. The Apple Watch also tracks sleep, but only if you wear it to bed, which brings back the battery problem. Many people charge it while sleeping, so they never get consistent sleep data.

Comfort is also a factor. The Flex is a slim, flexible band that you forget you’re wearing. The Apple Watch is bulkier, with a larger case and a display that can catch on sleeves. If you’re a side sleeper, the watch may dig into your wrist. I found that I slept better with the Flex, but I got far more useful insights from the Apple Watch’s sleep stages—when I remembered to wear it. That inconsistency is a common reason people switch to a dedicated sleep tracker or a hybrid device.

Smart Features vs. Simplicity

The Apple Watch is a full smartwatch: notifications, apps, music control, contactless payments, and even the ability to answer calls. The Fitbit Flex is just a step counter with a few silent alarms. If you want to leave your phone in your pocket and still see who’s texting you, the Apple Watch is the clear choice. But that convenience comes with a cost: more distractions, more setup, and more apps to manage.

For many people, the constant buzzing of notifications is the reason they switch back to a simpler device. The Flex only vibrates for alarms and goal celebrations, so it’s much less intrusive. On the other hand, if you’re paying for a cellular Apple Watch, you’re paying a monthly fee for a feature you may rarely use. The Flex has no such costs. The decision often comes down to whether you want a wrist computer or a wrist reminder.

Cost and Long-Term Value

Price is a major factor. A new Apple Watch costs several hundred dollars, and the latest models are even more expensive. A Fitbit Flex, when it was sold, cost around $100. Even today, a basic fitness band from any brand costs far less than an Apple Watch. But the total cost of ownership includes accessories: Apple Watch bands are proprietary and can be pricey, while the Flex used a standard clasp that was easy to replace.

There’s also the question of longevity. The Apple Watch receives software updates for several years, but the battery eventually degrades, and repairs are expensive. The Fitbit Flex had a non-replaceable battery, so when it died, the whole unit had to be replaced. Neither is built to last forever, but the Apple Watch’s higher upfront cost means you’re more likely to feel the loss when it stops working.

How to Choose What to Replace Them With

If you’re in the same situation—owning both or deciding between the two—here’s a practical way to think about your next device:

• If you want a smartwatch: Look for a model with at least two days of battery life, built-in GPS, and a heart-rate sensor. The Apple Watch is fine if you’re in the Apple ecosystem, but other brands offer similar features at lower prices.
• If you want a simple fitness band: Choose one with a screen (so you can see your steps without opening an app), a heart-rate sensor, and a battery that lasts at least five days. The Flex’s lack of a screen was its biggest flaw.
• If you want both: Consider a hybrid device—a watch-like tracker with a small display, long battery life, and basic notifications. These are often cheaper than an Apple Watch and more capable than a Flex.

The key is to list your top three priorities before buying. If battery life is #1, a smartwatch will disappoint you. If accurate heart rate is #1, a basic band won’t do. Most people find that they don’t need the full app ecosystem of the Apple Watch, but they do need more than the Flex offers.

Frequently Asked Questions

Can I still use a Fitbit Flex in 2024?

Yes, but with limitations. The Fitbit app still supports the Flex, but the device itself is discontinued. The app may stop receiving updates, and the battery will eventually die. You can still sync it via Bluetooth, but you won’t get new features or bug fixes.

Is the Apple Watch worth the extra cost over a fitness band?

It depends on how much you use the smart features. If you only care about steps and sleep, a $50 band does the same job. If you want to reply to texts, track workouts with GPS, and use health features like ECG, the Apple Watch is worth it.

Why does my Apple Watch and Fitbit show different step counts?

Each device uses different algorithms and sensors. The Apple Watch uses a more complex motion sensor and may calibrate to your stride with GPS. The Flex uses a simpler accelerometer. Differences of 10-20% are common. Neither is “wrong”—they’re just estimating differently.

Can I wear both an Apple Watch and a Fitbit at the same time?

Yes, but it’s redundant. You’ll get double notifications and double step counts. If you want to compare accuracy, it can be useful for a few days, but most people find it annoying.

What’s the best replacement for a Fitbit Flex?

Any modern fitness band with a screen and heart-rate sensor—like the Fitbit Inspire series or a similar band from another brand—is a direct upgrade. They’re small, cheap, and have better sensors.

How long does an Apple Watch battery last with heavy use?

With GPS and cellular active, you’ll get about 6-8 hours. With normal use (notifications, occasional workout), expect 18-24 hours. The battery degrades over time, so after two years, you may need to charge twice a day.

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