When it comes to fitness trackers, no-one sells more than Fitbit and Xiaomi. In the first three months of 2017, Xiaomi sold 3.6 million trackers and Fitbit sold 3 million devices. So a lot of people are choosing Fitbit, Xiaomi - or the fitness capabilities of the Apple Watch, of course - around the world.
For most people, the obvious difference in price will clinch it, and we'll look at that below. But what are the other considerations if you're deciding between locking yourself into Fitbit or Xiaomi? (If you think we're being overly harsh on Xiaomi, do let us know your experiences in the comments).
Fitbit v Xiaomi: Devices
Let's start with Xiaomi. You'll be looking at its Mi line which comes in a few options: the original Mi Band from 2015, the Mi Band Pulse (or 1s) from 2016 and this year's Mi Band 2. All three count steps and track distance with estimated calories - the main difference is that the second two track heart rate too.
The prices vary depending on the retailer but essentially Xiaomi trackers are amongst the cheapest you can buy and a fraction of the price of most Fitbits. At the moment, you can get the Mi Band for about ¬£10 and the Mi Band 2 for around ¬£18.
Moving onto Fitbit, there's a lot more going on and we recommend you check out our guide to which Fitbit you should buy. It details each of the trackers on sale, what they do and who they would suit. The absolute cheapest (RRP) is the Fitbit Zip at ¬£49.99 but it's pretty basic.
Otherwise, you're looking at between ¬£79.99 and ¬£199.99 for a Fitbit. They all use the same platform but each device offers a slightly different set of features.
Generally speaking, if you want detailed fitness metrics, go for the Fitbit Charge 2. Runners and cyclists should choose the premium Fitbit Surge. For style and everyday tracking, it's the Fitbit Alta HR; for a smartwatch alternative, choose the Fitbit Blaze. And swimmers can go for the water resistant Flex 2.
In terms of design, Fitbit offers more of a range of sizes, materials and customisation. They are also generally sleeker, though Xiaomi does a good job of keeping things light and comfortable. Both allow you to add new straps or bands after you've bought the tracker module and both make devices that are easy to wear all day and in bed without getting heavy or cumbersome.
Another big concern: Xiaomi tends to beat Fitbit on battery life with over a week and up to 20 days on the Mi Band 2 versus less than seven days on most Fitbits. Newer Fitbits like the Alta HR last a full week.
Fitbit v Xiaomi: Fitness tracking
We gave the last two Xiaomi trackers just three stars in our reviews mainly because we still don't consider the Mi Bands reliable enough trackers. It tracks activity in terms of steps, distance and estimated calories (for activities, not a helpful running total for rest like Fitbit) and heart rate if the tracker has an optical sensor. We've worn a Mi Band 2 and a Fitbit Alta together to compare the data and found that the Xiaomi is stingier at counting steps so bear that in mind.
In our testing, Xiaomi's algorithms seem to be slightly better at sleep tracking, which is also onboard. And again, the prices are so low that you might want to buy one just to see if keeping tabs on your progress works for you, perhaps before upgrading to a Fitbit.
So Fitbit is generally more accurate at tracking activity and workouts than Xiaomi, though if it's out, Fitbit tends to slightly overestimate - tweak the stride length to minimise the chance of this happening.
There are all sorts of additions to make Fitbit worth the money, though - again depending on the tracker you can use GPS, connected GPS, VO2 Max, workout modes, more control over heart rate tracking, breathing exercises and auto workout tracking. Again check individual reviews for detailed testing and consideration of what you get in which device as it really does vary.
It's hard to test sleep tracking outside of lap conditions but Fitbit tends to be accurate at estimating when we fall asleep and wake up. Its trackers also spit out a lot of data on light, REM and deep sleep for data nerds.
Fitbit v Xiaomi: Apps
Xiaomi's Mi Fit app is about as simple as you can get for a fitness tracker platform. We have found it not only slower to sync than Fitbit but also more prone to crashes on Android. As for what you get, there's a dashboard which has recently been revamped. It shows your day's steps as well as last night's sleep duration, your latest heart rate reading and a button to track your weight manually within the app.
In terms of motivation, it allocates winning streaks for when you hit targets and lets you share progress via Facebook, Line and Twitter (messages). The views available are daily, weekly and monthly for activity and sleep but heart rate is disappointingly treated separately so you won't be able to see a handy chart of this in the same way as distance.
Fitbit is, in many ways, the most comprehensive and most successful of all the fitness platforms. It doesn't do everything, of course, but it's easy to use for beginners, offers the opportunity to dig down into trends and workouts for dedicated runners and gym bunnies. Plus it's very social and that could make all the difference for your fitness goals.
Read this: A beginner's guide to Fitbit's ecosystem
We won't list everything here but the main advantages over the Xiaomi app are the ability to log water, food and not just weight; you can link up multiple Fitbits to one phone and most importantly, the motivational social badges to earn and Challenges including the new Adventures for the 2017 trackers which give you step/distance goals based on famous.
There's also a lot more info in the sleep tracking section, including the new insights (for everything apart from the Zip) which are starting to offer actionable tips.
Fitbit v Xiaomi: Extra features
Don't buy a Xiaomi tracker expecting extra features beyond health and fitness tracking because you'll be disappointed. Here's what you get: smartphone notifications as a vibration for certain apps and these are actually too hit and miss to rely on. Oh and it displays the time plus you can set alarms.
You could check out the more expensive Amazfit line of watches and smart bands (made by Xiaomi's manufacturing partner Huami) for more of a straight Fitbit rival.
Fitbit does better here, as you'd expect. Depending on which tracker you choose, you can get real onscreen smartphone notifications (with vibrations) for calls, texts, calendar and third party apps like WhatsApp and Facebook. This can be more readable and useful on certain screen sizes/orientations than others so bear this in mind. Fitbit is also due to launch its app store later this year alongside the much leaked Fitbit smartwatch, potentially changing how we use Fitbits entirely.
Fitbit v Xiaomi: Verdict
Sorry to circle back to it but the biggest factor in your decision, after reading our guide to the two platforms will probably still be your budget. In most cases, if you expect to be using a fitness tracker for a long time, pay the extra and go for a Fitbit or another of our recommended best fitness trackers.
Xiaomi is more of a beginner's fitness tracking option, there are set up and syncing pains, not to mention the reliability problems we've encountered. No activity tracker is 100% accurate though so if you'd rather spend less full stop, and get extras like that impressive battery life, just take the gamble on a Mi Band.
Fitbit and Xiaomi sell a hell of a lot of activity trackers but we would suggest you widen your search to encompass the latest Garmins, hybrid watches that are essentially fitness trackers from Fossil and other designers, plus options from Misfit and Moov. Essentially, broaden your search and you might find that the perfect tracker for you isn't the perfect one for three million people, and that's OK.