I think ultimately this is a question you must answer for yourself. I have a fixed screen (snaps all the way around) and its not perfectly flat and from time to time it drives me nuts. Honestly, the casual observer can't see any defect in it at all -- I'm pretty picky.
A suggestion would be to save all of the money and put together a cheap DIY screen and use it for a month or two. If the "defects" in your DIY screen bug you a lot -- you'll have your answer.
I own a "real" screen and I'm happy with it -- however, if I were doing it again I'd either get a better screen (ie: more expensive), or go the DIY route.