I'm top tier in all 3 alliances. As for ST, I fly them a lot due to the destinations and hubs at CDG, AMS and NBO mainly. But I get pretty decent service. For RTW's I don't use ST often due to the fact that I don't need to go to Korea often. If they added MH, I would take more ST RTW's, but for now I use Star or OW.

As for an overall rating, I rate OW as the best mainly due to more flat business seats and great lounge programs. Star and ST are roughly the same in this regard, at least for someone based in Europe.