I too have heard of lightgun problems w/ flat tube TVs. If you plan on using lightguns, be sure to research that first or you might be dissapointed.
Seems to me like a trade off...
Flat tubes require no bezel
Std tubes have a more arcade aesthetic because that's how arcade monitors were (i.e., not flat).
Bezels are cheap from Happs.
Do you already have a cabinet, or are you going to buy one, or are you going to build a cab around your TV? If anything other than the last option, make sure that the TV will fit! It's getting harder & harder to find any flat tube TVs that do not have speakers on the sides of the tube. What this means is that you will have a smaller diagonal TV if you got flat & put it in a cab since you have to accomodate the speakers.
std tube TVs are also a bit cheaper. If I were doing something where the TV is NOT in a cab (say something where the controls are on a pedestal & the TV is on a pedestal - like this -
http://www.dreamauthentics.com/el_gallery.html ) then I would use a LARGE flat tube. Anything else I would go with a std monitor, but that is just me.
One thing I noticed when switching from a std tube to a flat tube for my main home TV:
The flat tube tends to present a crisper picture. It also has a more pronounced screen door effect, but after a couple of weeks you don't notice the screen door effect anymore.
Normally the crisper picture is better, BUT those old arcade games had low res, blurry pics, in which case a std tv tube might give you a more authentic feel as well, never mind the actual shape of the tube.
Brain21