What tracks burn better, wrist tracker or gym machine?

Note: I am not familiar with either the Precor equipment or the Gear Fit 2 equipment.

In general, though, I believe the trackers that we buy are able to be more-so customized to our specific attributes; which I believe would give more accurate readings as a result.

It's all estimates. My personal rule when starting out was to evaluate multiple sources of info (machine, MFP database, other more sport-specific online calculators, my tracker/HRM) and, if I didn't have a reason to prefer one as likely more accurate, to pick the lowest one.

Keep in mind that the overall recommended process here is to log carefully and consistently for 4-6 weeks, using your MFP calorie goal and eating at least a good chunk of your exercise calories. Then, evaluate your average weekly weight loss and adjust intake as needed so as not to lose to fast, but to keep losing at a sensible rate.

In that kind of context, it's more important to be consistent in how you log exercise (same method for the same exercise every time) than it is for the exercise estimate to be individually exactly correct.

I use my tracker or HRM for most cardio-type exercise (with a level of skepticism for interval training ), MFP database for things that heart rate is a super-poor estimator for, like stretching/yoga or weight training. (My Concept 2 rowing machine has a decent rep for calorie accuracy, once the C2 online weight adjustment calculator has been applied, but it's not enough different from my tracker/HRM most of the time to fret about, in practice.)

This is an oldie but goodie about understanding the limitations of heart rate monitor estimates:

https://www.myfitnesspal.com/blog/Azdak/view/the-real-facts-about-hrms-and-calories-what-you-need-to-know-before-purchasing-an-hrm-or-using-one-21472

Best wishes!

I have a Fitbit charge 2