i think either would work. i have seen both two 4:3 and one 32" vertical. check out this post from my fav ki lover. has punchout running on a 32".
what monitor type are ya gonna use. arcade, pc, or tv and how will it be hooked up?
the linked post below is with a 32" crt its the same thing im thinking of doing.
the only draw back i could see is if you planned on just using onboard video to drive the system as you would need to make sure the mobo has two outputs like vga and dvi.
Thanks to Cheffo, I had to see how well punch out looked, 2 monitor outputs spanned across a 32" vertical monitor dont look too bad!



Also works pretty good with Playchoice 10:

Vertical goodness!
[img width=640 heigh