Of course the best indoor trainer is the one that you will use. The others (i.e. the ones you don’t use) are too expensive, even if they are (practically) free. 

FWIW, I’ve been using the Peloton for the last couple of years. For me, I like the “Spin Class” vibe when exercising indoors (I guess that makes me not a particularly serious cyclist).

I’ve used Zwift briefly, but I think that riding inside is almost a different activity than riding outside. I really like the Peloton. It is expensive for the equipment and for the monthly class subscription, but they have a “Power Zone” training program where you take an FTP test, then do workouts that target a specific power zone. I found these incredibly helpful as you know exactly how hard to work. I can get a good workout in a relatively short period of time. My power has certainly improved in the last couple of months that I’ve done these rides. Another advantage of the Peloton program is there are also classes for stretching, strength training, yoga, and even meditation. I think they really do have a lot of great instructors.

With that said, I know that it isn’t for everyone, and I would encourage you to try it out if you can. That applies to Peloton or a trainer for Zwift or whatever. I’m certain that someone on this list has a bike trainer that you can borrow and try some of the other options.