I've gone through a fair number of fitness watches, and have a large number of friends with the others. (I'm in a field where just about everyone I work with works out 3-7 times a week).
I've been exceptionally impressed with the Garmin watches. For the 300 range, a Garmin Vivoactive 3 is a very good choice. If you do the types of exercise where the features make sense, a Garmin Fenix 3 off ebay or refurbished is in the same ballpark for price. It's also an excellent choice.
If you want to focus on Gym workouts and tracking for that, the Vivoactive 3 works *fairly* well. If you're doing crossfit, then it's more of a pain thank it's worth to track the workout in terms of rep tracking and the like, but if you are doing weights or other individual workouts, you can track those if you configure in advance. It's got some ability to track reps on its own and you would just load the weight afterwards, but really the vast majority of fitness watches are cardio oriented. There's a couple of gym targeted watches out there, but they're still quite bulky, and are one-off products, that is to say I don't know of one dedicated for gym work from one of the big 3, Garmin, Polar, or Fitbit.