Second Life is best life.
I've spent maybe $50 in SL and I've played it for years. I've played as different people, and had a lot of fun. You can get started in SL for free, and learning the ropes isn't all that hard.
The only thing that I think is lacking in SL is people. There is just too much space and too few people to fill it. Not that there aren't plenty of people, but they are just too spread out.
I have played Yareel, and Sexpexfex, but there is absolutely no depth to them and all you get are the same series of animations over and over while they beg you to spend real money in the game. Second Life offers more variety, at far less cost than either of those.
Second life is superior.