I don't think it is possible to say which program is best. Each one has its plusses and minuses. I like Marriott because of the plethora of properties, the US Renaissance Inns can be fun, the Residence Inn is one of the best long term properties and the best if you intend to cook, although its free breakfast is unremarkable.

I also like the fact that Marriott makes nearly all of its rates availabe online.

Marriott's downside, for me, is actually the Marriott line which I find fairly arbitrary although improving.