I have an MDF router. Not a big mistake if you want something to "learn" with. Big mistake if you actually want to do some serious cutting, though! And in the kind of size you are looking at, MDF thick enough to have some kind of strength(*) will just make the whole thing too clumsy.
(*) Strength - until it gets damp/humid/tired/too hot/too cold/there's an R in the month...