[Ben Harmless]

My thinking is that it very much depends on what else you'll be doing with the room.

Hardwood floors can be nice for getting more of the room's sound back into the mic. The only thing you have to worry about in that case is whether or not you like the sound of the room when it comes back into the mic, and you won't know that untill you try. If you do happen to like it, then great. Experiment with different amp and mic placements and have a blast. Just remember that it'll be hard to keep that natural reverb out of the mix should you want to do so.

With carpeting you'll obviously get a lot more sound dampeniing. However, the room still has walls, and so you shouldn't expect a perfectly dead environment just because you have carpeting. You probably knew that though.

Where it gets tricky is when you have other things in the room. It is going to be a guest room? If so, you'll probably have a big bed in there that will affect the sound. If there's a lot of other furniture, it will be further affected.

Unless you can have to room all to yourself, my approach would be to keep the carpeting and try to deaden the room a little. Then you can spice up your recordings with a little reverb from a processor. It's not ideal, but most pro recordings aren't made in big open spaces anymore anyway. Heck, the last thing I recorded was for national release, and we did it in some guy's attic.