Most of these points have been made somewhat, but here's the deal:
We are #1 for Russell. The only other "major" teams they do currently are Ohio, Samford, Western Kentucky, and Southern Miss. The other big thing is the Harlem Globetrotters. They did, however, do all the uniforms for MLB from 92-97 and during the 90s for a number of NFL teams (including the Falcons, Cowboys, 49ers, Packers, Patriots, and Saints).
We would mean much less to other companies like Nike (44 of 65 power 5 teams), and maybe even Adidas (12), and even UA (8). I don't think anyone doubts that Nike could care less about what we look like.
UA could be a good change - You would have to think we'd be more important in the pecking order than Cincy (maybe around even with them), Navy, South Florida, Temple, Boston College, Northwestern, Toledo, Colorado State, Hawaii, and Utah. We'd be behind Maryland, Texas Tech (maybe close to even with them), Notre Dame, Auburn, and South Carolina. For Adidas we'd be even with maybe Louisville (maybe not counting basketball) and NC State, we'd be behind Miami (at least their brand), Michigan, Nebraska, Wisconsin, Kansas (if only for basketball).
And let's not forget, WE have just as much control over style as Russell. If WE didn't like a style, we could easily tell Russell that we want something different (or shop around to someone who could do that). Obviously WE (the school) are satisfied with Russell and the look of the uniforms. Otherwise we would seek a change. If we wanted to go with the simple old school look that Mack likes that should be pretty easy to do (remember the jerseys below?). Clearly whoever is in charge at GT likes the more modern look.
So if the thought is "I don't like the way the Russell Jerseys look," ask yourself whether the first jersey below is ok for your taste. Cause it was made by Russell. Clearly they are capable of making whatever jersey we want; it's GT who decides the full look.