Trials Wheel size? 20? 26?

I am going to get the BEDFORD HARD CORE MONTY TRIALS, but I would also like to use it for Muniing. I’m more interested in trials than I am in Mountain, so will the 26" tire on the Hard Core cut back much on it’s performance or what? How will a 20" perform in Muni conditions? Is it worth spending an extra $75 for a 26"?
Please help



build a decent 24" that you can use for both.