I bought the Galaxy Watch Active 2 a little over a year ago. I was hesitant at first because it does not have MST. I use MST at my local store since they have not adopted NFC yet. I was also worried the lack of a physical rotating bezel would be a problem.
After almost a year I can say even though the watch has compromises it's still a very nice watch.
Since we have been social distancing I have been running outside almost every day and this watch with it's LTE has been all I have needed to take with me which was the original reason I started writing apps for Samsung's wearables. I track my runs on it while either using Alexa to listen to the radio or using the Spotify app to listen to music. And when I'm done I use Alexa or my Wink app to unlock my smart locks. On LTE, the tracking and media playing takes about 1% battery per minute. This is about the same as what I experienced on the Gear S3 on the limited testing of this I did on that watch.
I have two complaints. The GPS would on occasions freeze up during my runs leaving me to guess how far I've gone based on time and the automatic transition from Bluetooth to LTE could be smoother. I either have to explicitly cut Bluetooth on my phone or wait until I was out of range and another 30 seconds before LTE would kick in.
I have a Bluetooth Galaxy Watch 3 for testing and can say now that a physical rotating bezel is easier to use. It also provides extra protection as I found out my watch "scratches at a level 6 with deeper grooves at 7" after I accidentally rubbed it against our granite counter top.
All in all the Active 2 is a really nice companion for outside activity while as with every other smart watch a way of distancing yourself from your phone without completely disconnecting. If you had to choose between this and the Watch 3 I'd probably for now choose based on size and look. The Active 2 is a lot smaller than the Galaxy Watch 3.