I think the reason it keeps getting asked so many times is because everyone is looking for a definitive "right" answer, and there isn't one.
MDO sounds great -- if I can find some. My local lumber yard has MDF and plywood. All these and more have been used successfully, they all appear to have pluses and minuses. I still haven't decided.
You might find this amusing. . . I corresponded with someone who is in business making custom MAME cabinets. His opinion, unfiltered: "I prefer particle board it is strong and with 1 coat of primer ans 2 coats of paint iit should last forever.I could use MDF if wanted?It doesn't cost that much more.I've used both before and it really doesn't matter.If you are planning on using t-molding you can't use plywood.Its not solid enough to router the hole."
Somebody asked about using unconventional materials like metal or plastic. It's an interesting idea. I think it would be cool to try building a cabinet out of honeycomb sandwich panels. It would probably require epoxy to hold together in key places (kind of like a big model rocket), I don't think wood glue or screws would work. The edges would have to be finished with something other than T-molding, I'm pretty sure.
The resulting cabinet would be easy to move around, but it would be so lightweight that I wonder if it would be stable during gameplay. I wouldn't want somebody giving it a shove and knocking it over.
