For the most part they are the same machine, same frame, cab, engine, etc. The main differences between them are, Dump Box, Clutch springs and weights, Turf Mode, Front grill / Front body panels, Acoustic mat on back wall, DESS Key. When you get into model specific differences, they will have things like HMWPE underbody protection, synthetic winch rope. etc.
The dump box makes it easier to work on the engine, although other than plugs and a valve check there is not much required in terms of engine work. oil changes are about the same. A downside of the dump box is it is out past the rear wheels, making the machine longer and can get hung up and damaged coming off ledges and obstacles. You can swap the dump box for the sport bed if you find you are having problems getting caught up on things.
The clutch in the Commander leaves a bit to be desired. BRP went a bit overboard on the utility side of tuning the clutch. You can install the Sport clutch weights and springs in the Commander or get an aftermarket clutch kit.
Turf Mode is amazing on the lawn and asphalt. Although I do not believe it is as robust. I have heard people having problems with turf mode but could be operator error. You must stop before engaging or disengaging Turf Mode.
I prefer the grill and front body lines on the Sport and Trail over the grill on the Commander, but that is just personal preference.
The Sport is not bad for heat and noise, it will be vastly quieter than your 2019 X3. The acoustic mat helps on the Commander and can be added to the Sport.
Both are great machines; it depends on what your intended use is.