I guess it depend from person to person. In my case I don't like too much unpredictability and the mentor roulette is so random. In other roulette types I get more predictable parameters despite the duty randomness.

My prefered roulettes are expert+lvl cap because I got my entire toolkit, normal roulettes because im guaranteed lilies and it has many fun duty options. Trial roulettes are also among my prefered though I like normal more.

I love alliances from wheeping city and up but usually skip that roulette cause CT...CT...CT