real games don't have plexi
Original Neo Geo CPOs were 1/8" plexi with the artwork silkscreened on the bottom. Take a look at any nintendo classic (Donkey Kong, Popeye, etc).. Plexi with silk-screened artwork..
I'm sure people could come up with more examples. Real games certainly did have plexi.
Every "real arcade game" I remember had plexi added by the operator, so to me, real arcade games do have it. The one's that have survived, at least.
"Real games" were built as cheaply as possible - out of particle board, silkscreened artwork where the plates didn't exactly line up.. I would think a DIYer could do better.
It's a matter of preference, in the end. I prefer the feel of smooth plastic to rough vinyl or cold metal.
I decided to spraypaint the CP on my neo geo, after figuring that getting the red and white paint masks cut was cheaper than having a CPO reproduced (would have to be custom for my 19" "gold" cab that I've redone in red). So far it looks amazing, much better than anything that rolled out of the factory, and I'll definately cap it off with plexi for the both the right "feel" and to protect it.