Without question, health trackers can help you improve your performance and meet your fitness goals. What’s more, clients will look to you as their fitness guru to help them maximize their use of trackers.

With so many health trackers on the market today, choosing the right one can become a complicated task. How can tracking your sleep patterns improve your overall health? Do you want to compare your resting heart rate to your active heart rate? Do you need a GPS feature to track distance? Are you tracking your food intake?

Here, we take a look at four of the most popular wearable health trackers of 2015 and compare their features.

With its continuous heart rate monitoring, the Fitbit Charge HR ($150) can offer more accurate feedback on your activity and calorie burn than other trackers.

The Charge HR provides data on steps taken and calories burned by day. It monitors heart rate during workouts and while at rest. It also has a stopwatch and sleep monitor. Unlike older Fitbit models, you don’t have to tell it when you’re going to sleep—the device’s sleep mode will kick in from your movements and heart rate data.

The Charge HR design is unisex and comes in three sizes to accommodate wrists of different sizes, though—caveat—users have complained of skin irritations after workouts. The screen is bright and easy to read, despite being the size of a fingernail. The Charge has a caller ID feature, where the band buzzes when someone calls your smartphone and the name of the caller appears on the screen.

While the Charge HR provides superior health data, there is no GPS feature. The wearable cannot even estimate distances. While this is detraction for runners and cyclists, the Charge HR is well suited for in-studio workouts.

The UP4 by Jawbone ($200) is super chic and a clear winner when it comes to fashionable design. Because this tracker has no screen, you have to monitor your fitness data through the Jawbone app on your smartphone. But the UP4 was meant to wear 24/7 to give you a more holistic picture of your activity and health, and its battery lasts for days, not hours.

The UP4 has a heart rate monitor, activity tracker and step counter. The wearable measures calories burned, hydration level, and the temperature of both your skin and your surroundings. You can use it to log your meals and track calories in no time with a barcode scanner, restaurant menu search and food database. It also has a program for goal setting.  

One of the features that sets this wearable apart is its robust sleep tracker. The UP4 can track your true sleep stages—REM, Light and Deep. Smart Coach is then able to give you suggestions to maximize your sleep and improve the quality of your days. Another unique feature? The UP4 can be used to make American Express contactless payments, which is convenient for buying a juice or snack on the go.

The Jawbone UP also comes in two other models that are less expensive and have fewer features.  If your tracker needs are fairly basic, you may want to check out the UP2 or UP3 as good options.

One of the biggest selling points of the Withings Activité Pop ($150), besides its retro-cool analog watch design, is its eight-month battery life. Plus, the tracker is water resistant, meaning it can be used while swimming and worn in the shower.

The Pop tracks steps, distance and calories. It automatically detects when you are walking and when you are running, then breaks down the data by activity. The Pop’s sleep tracker also detects when you are asleep and keeps track of light and deep sleep stages, the number of times you wake up and the total duration of sleep. You can also set an alarm to a gentle wake-up vibration. And if you change time zones while wearing the Pop, it automatically resets itself using your phone’s time setting.

The wearable works with the Health Mate app, which features activity badges, a leaderboard, healthy reminders and activity insights.

The smooth silicone strap is both comfortable and durable no matter what activities you put this wearable through. You can also purchase a variety of straps to update the look of your Pop. 

The Garmin Vivoactive ($249) is the more than just a health tracker: It’s like wearing a surprisingly lightweight data center on your wrist.

In fact, the Vivoactive is more like a smartwatch than a fitness tracker. In addition to tracking the typical information—steps, calories, heart rate, pace, distance and sleep—the wearable also delivers all of your smartphone’s notifications to its color touch screen. These features include calendar reminders, Tweet notifications and missed text alerts.

While the Vivoactive may not look as sleek as some of the other trackers, it does allow you to access your fitness data in real time, without having to check your smartphone. The Vivoactive has robust apps for running, walking, cycling, golf and swimming, making it more versatile than many of the other available trackers.