spas in home or in lots?

On a community lot but I have used them on a home lot too.

I mainly use the lot -- I'll send my active Sims there after a workout session at the gym especially if they have the Sore moodlet. I'll occasionally add a yoga/meditation room to my houses when I add a basement.

Both. On my home lot as a cooldown measure after using the home gym and on lots as part of a spa lot.

I would have my sims use the lot, but some more affluent household may have a home gym and sauna. Some sims may have the yoga mat or stool at their disposal.

I prefer both. For my smaller homes, my Sim always has a spare bedroom with space for either a yoga mat or a meditation stool. I also like to have her visit the community lot so she can be there either alone or with a yoga club.