I'm still pretty new to this but I'm finding that it's really a case by case basis. I love my C.O. Bigelow cream (proraso), but I also love my Tabac soap. I don't think it can really be said that one is superior to the other in such a general sense as far as performance goes.
My favorite would have to be creams.
I started out with soap, but I never had much luck getting a really good lather and when I could achieve said lather it look ages to build.
Where as creams, a few minutes in a hot mug and I have loads and loads of soft fluffy cream ready to go.
I prefer soaps. Even though it takes a little longer to build lather I get a closer shave. I like the inexpensive Col Conk soaps the best they seem to be slicker than the others. I haven't tried the Mama Bear soaps but they are next on my list.
I was going to say soap, but upon furthter evaluation, I have to say both. I have been making superlather lately using VDH Glycein and Proraso, or KMF lavender. I think I get the best results this way.
Like others, I like the challenge, the ROI (more shaves for the buck even on the high end and/or pricey soaps), and the fact that you can easely have 15 soaps in rotation without having to worry they go bad.
I'd imagine that most of us have both in the den, even if we have a strong allegiance to one or other. Neither of them pose challenges sufficient to avoid using them and its nice to have a change when the mood takes you. For me, I spent the last week using a straight and creams seem a bit more stable, allowing me more time to concentrate on the cut, rather than nursing a bowl of lather. I certainly have one brush which has been designated for creams and one I'll tend to save for soap. This is purely an arbitrary disctinction and nothing to do with the limitations of the brushes themselves, but sometimes I want to pamper myself, so I'l get out my Kent H8 and some L'Occitane cream. Othertimes, I think "I'm not into all this effete nonsense. I'm a real man!" and bring out my Boarbrush and MWF.