This is a HUGE deal to me, I'm surprised we don't hear this mentioned more often...
Basically, the old norm and/or status quo was that for best accuracy handgun sights with smaller gaps on either side of the front blade ("light-bars") when viewed through the rear sight's notch were best, kind of the reason that pretty much to this day most handguns come with sights where the front-blade-width is about the same as the rear's notch-width. Whether it's a 1911 with a front blade that completely fills or is actually wider than the rather narrow .115" rear Bo-Mar-type notch, or a Glock that gets a wide .160" front paired to a .140" rear notch (factory Meprolight Tru-Dot NS).
The general reasoning was that smaller light-bars meant less chance for the front blade to "swim" causing poor accuracy, thing is, small light bars take a lot longer for our brains and eyes to line up, and as it turns out more light around the front blade (bigger light-bars) actually makes it easier for most and is just as accurate.
It's been discussed by many competition shooter's for a while now that a perceived light-bar roughly 1/2 the width of the front-blade at one's normal arm's length shooting stance is optimum for both speed and accuracy, so this varies with different individuals eyesight and body dimensions (i.e. short vs. long arms, etc.).
The winningest sights used by competitors in both IDPA and USPSA these days seem to back this up, as the Warren/Sevigny sights used by Sevigny, Vogel and countless others are clearly the most popular with lots of companies jumping on the bandwagon and putting out "QWIK" or "wide-notch" options these days. What's important is the ratio of front-blade-width to rear-notch-width, Warren/Sevigny's for example are usually a .115" width front sight paired to a .150" width rear notch, usually on a gun with a longish 7.5" sight-radius... that's lots o' light around the front-blade, guys like Sevigny and Vogel seem accurate enough to me, at least compared to most humans.
Of course,
"different strokes for different folks" applies, for instance: I'm not a fan of night sights and don't really consider them really a necessity, with this in mind, I've been able to experiment with lots of different widths and have found I prefer my front blades to be a pretty skinny .090" which I match up with a rear notch of .125" (same exact ratio as the Warren/Sevigny's, just a narrower "window" with a front that obstructs less of targets at longer distances which
for me helps a lot), now that said, I know plenty of guys who won't own a gun that's not equipped with tritium night sights and in that case front-blade-width is usually limited to either a .140" or sometimes a .125" front, so if one wants the same light-bar ratio they'll need a wider rear notch too (until recently this was a PITA to find, but these days Ameriglo and maybe a few others make rears with notches in all kinds of widths, some just plain ridiculously wide actually)...
It should be noted that different sight widths, even at the same light-bar ratios, don't transmit exactly in relation to distance, and there are pluses and minuses to going either way (skinny vs. thicker). Wider fronts with really wide rear notch's (say over .150") may be real fast and kick-mucho-ass in close, but groups on a 25 yard target shot using a .140" front are probably not going to be as tight as groups shot with say a .090-.100", so scaling one's "window size" to what works best for the type of shooting accuracy one is looking for at given distances should be a consideration.
- Sorry for the novel, this is just something that interests me a great deal and something I've done a lot of research on, guess I'd probably pick a shittier gun with good sights over a better one with shitty sights if I had to. Don't even get me started on whether "loud" eye-catching sights are really better than uncomplicated, uncluttered plain all-black irons...