Sounds like Ford vs Chevy debate....
After having gone through this very recently, I chose a Billy Cook all around for my own reasons. However, that being said, the main purpose for my needing (yes, "needing") a new saddle was that my other two saddles did not fit my 2 horses (saddles too narrow, horses too wide). So, after much research and talking to a few saddle experts, I learned alot about fitting a saddle. So, no matter what brand of saddle you decide upon, its really important that it fits the horse that you're going to put it on, or at the least is a very good fit for an average horse if you'rs is average. There's a lot of Mexican saddles being sold around here (and on eBay)for cheap, cheap, cheap, but they're built for a narrow horse and won't correctly fit a typical quarter horse. My thought was, that if I was gonna invest in a new saddle, I ought to suck it up, fork out the bucks and get one that will fit both my butt and my horses' backs. I mean, its an investment that will last a lifetime if properly taken care of so I might as well do it right.
Anycase, here's a site that will help with measuring a saddle:
http://www.arcaros.com/treemeasurement.htm
There are others out there that get pretty technical with measuring a horses back and form fitting saddles to that measurement, but I wanted something that would fit a few wide backed horses, not one in particular, so I went for the average full quarter horse bars of the Billy Cook Roper (all around) as I found out that the Billy Cook Ropers are about the widest saddles made and a little wider than their trail saddles. Of course, to make things more difficult, I found out there are no standards when measuring for full QH bars vs say, semi QH bars, so it makes finding a well fitting saddle even more difficult. Most saddle shops (even the internet ones) will let you take the saddle and try it on your horse, providing you don't get it sweaty or muddy.
All in all, a correctly fitting saddle does make a difference.