Well, I think everyone's going to say it, but I have to as well: I'll listen to whatever's good.
That said, I think that a really good band has the potential to be better than a really good solo artist. I'm of the school of thought that feels that collaboration is one of the most powerful tools at any artist's disposal, and all a band is, is one big musical collaboration spanning many years, many albums, many concerts.
I love to see how the different band members push and pull off of each other to (hopefully) create something that no one of them could possibly have created on their own. Sure, sometimes "too many chefs ruins the soup," but in most cases I think the more talent a band has to draw from, the better.
Of course, bands have their down side, too. We can all think of a time when there's been a great band we love, but it has that ONE weak-link member who just isn't quite up to the talent level of the rest of the band.
There are also instances when one member seems to seize total creative control of the band. This can have some very good results (think Roger Waters' Pink Floyd) but I think it's never as good as what the band COULD have come up with if everyone had had a little more input into the direction the band takes.
I also find it interesting to follow one person's career as they move from band to band and project to project, seeing what they can do when paired up with different people in different environments. Audioslave is a perfect example of what I'm talking about, Dan the Automater's career being another.