Hmmm... 21" tv , composite video connection , eyes only a handfull of inches away from the screen. Will you be including complimentary prescription glasses for the tikes ?
Whew.. I feel a headache coming on just thinking about it. Actually I've never built a cab using a tv so I have nothing to go by but seriously do you ever experience eye strain with your s-video cab or is it just an old wives tale ?
Its a wives tale.
The original monitor was a 19" GO7, so a 21" TV is not like I threw a 50" Sony Vega in there. I have an S-Video 27" TV on my other cab and I don't have any problems with headaches or eye soreness. Really, what's the difference if the TV was big or small, you are still going to be the same distance away from a TV. If the images were so big that you couldn't track them without turning your head, then you'd probably have a problem. The difference between a 25" CRT arcade monitor and a 27" TV w/S-video from 3.5 - 4 feet away is not that big a deal, especially when the vertical games get cropped by mame to fit the screen. Horizontal games are awesome, too. Believe me, you haven't played a game of MK3 unless you've done it on a big screen.
I have a 21 Inch Computer Monitor that does not give an accurate portrayal of the games, in my opinion, of course. The picture is TOO good. You can begin to see the sprites and the images of Donkey Kong, Pac man, and others look very bit-mappish for my tastes, even with the scanlines feature. I will admit that the composite is not the answer, but now having seen everything but Component TV, I like my S-Video solution. Of course, nothing is more realistic than an arcade monitor, but TV's are generally cheaper and prior to ultimarc's Arcade VGA, a pain to hook up.
Just my 2 cents. Of course, everyone's tastes are different.