FWIW I’ve ridden each of these a fair amount:
- Kaiser M3i (hotels and gym near parent’s house)
- Spinner NXT
- Freemotion S11.8
- Stages SC3
For your wife I’d say they are probably equivalent.
Buying for myself? The Stages hands down, followed by Freemotion. My least favorite is the Kaiser.
And like others have said, I’d rather go with putting bike on trainer. Thats what I plan to do the day my wife is ready to ride.