To make things even more complicated, consider combos as well.
Birch to me is sort of the standard. I like poplar due to the lighter weight, but I like the tone for birch. Many of the well recorded cabs are all birch. The only cabs I have used that were Poplar are Carvin cabs. Good cabs, but I like Mesa's and ENGL's more. Bracing, sealing, insulation all play big roles.
Pine was used in older fenders and Budda uses pine. Very thick tone.
I have an Earcandy 1x12 that has a Birch Shell with Mahogany front and back (I think it is the standard now). That cab rocks! Sweet sounding with any speaker I have put in it. I have another with a pine shell/birch cab and the mids are thick and cut like knives. Could be construction and porting also, no insulation.
MDF I would assume you would hear more of the speaker and less of the cab. They are common in HiFi speakers. Unfortunately they are often used in cheap cabs with cheap ass speakers. Since they don't hold up to moving and are heavy as hell, they are poorly regarded. I would be interested in hearing them as a guitar studio cab though with nice speakers, good jointing, and bracing... hmm... maybe a weekend project.
