when I setup my first first triplehead rig..
I had 3x 20" dell 4:3 monitors. and my current rig for the past year is
3x24" 16:10 monitors.
in terms of the field of view and perreferial vision 3x4:3 and 3x16:10 is not really noticable.
I do notice it's a wider fov but not something that I would go "WOW" over.
in actual gameplay it doesn't really matter and there's no advantage to me of 16:10 over 4:3.
it's like playing a game at 75 fps vs 85fps. 85fps is better but at that point it really doesn't matter that much.
I personally perfer 3x4:3 over 3x16:10/16:9 for producitiy and work reasons.
one downside of 4:3 is that the HUD elements sometimes get cut off and go into the next monitor
here's an example (my old setup)
where with a 3x16:10 all the HUD elements fit in the center monitor. (my new setup)
that's the only disadvantage of a 4:3 setup but it have more to do with the individual games.