As for wheel on / wheel off - I believe most wheel-on trainers need to be calibrated every time you use them, whereas I calibrate my kickr about once every other month with no particular issue. Wheel off usually is capable of simulating steeper grades, which may or may not matter to you. No wear and tear on your rear wheel so they're also cleaner to run in your den or wherever.
I personally like zwift because seeing some fake guy go by me on a fake bike motivates me to ride harder than watching a show on TV. Trying to keep up with a fast group, or a race is motivating too. YMMV. I can't STAND indoor trainers for more than 30 min normally but somehow I can tolerate 4 hours on zwift. Go figure. Trainerroad is superior if you just want to do hard core workouts though.