What its made of isn't that big a deal really unless you're a bass player because sometimes they have ported cabs so then the sound of the cab itself comes more into play. I wouldn't worry about it too much.
Actually most guitar cabs are made from plywood strictly for the strength/weight ratio. MDF is better for sonics but is heavy and brittle compared to plywood. Cabinet resonance does add to the sound you hear. If you don't believe me listen to the back of one sometime. The ideal cabinet material would have no resonance at all, but this doesn't happen in the real world.
This type of cabinet will tend to impart its own "sound" on everything you play through it - more than most cabinets already do. Great if you like it, and that's what you're going for. If you want something very versatile this might not be a such a great attribute.
Most drivers designed for guitar cabs also have their own distince sound.
Some cabs are made from partical board, some from plywood, and not many from solid wood. Best choice is probably plywood; it's lighter than partical board and stronger than the other two.