I played in HS football Utah and Arizona (granted 10+ years ago), and I've
watched many high quality games at all levels in the state of Arizona, Utah, and Texas. The thing that stands out in Texas from Arizona and Utah is the pageantry, athleticism, and speed. I think Utah has really great loyalty and support for their teams, and I enjoy watching the games. Arizona has a little more athleticism and speed than Utah. But, I honestly was blown away by the speed in Texas. Even really bad teams have serious speedsters.
For example, Britain Covey in HS was special because of his VISION combined with his speed and athleticism, but his competition week in week out was not as athletic. In Texas, 3A-6A in both DI and DII as well as various 1-2A teams have 10+ guys with Britain's speed, 5+ guys with his athleticism, and 1-4 guys with his vision. These guys come in all sizes from 150 lbs scat backs/QBs to 245 lb. TE/LB/RBs. Don't get me wrong, I love Covey and there are good athletes in Utah. But, my anecdote is that the quality of competition in regards to athleticism vs. athleticism is better in Texas at large.
It is a shear number thing. You're right that these athletes largely reside in the greater metropolitan areas of Houston, Austin, San Antonio, and Dallas. There are quality teams outside these regions too, but the greater Houston area alone is more populous than Utah as a state.
Arizona has more overall speed and athleticism than Utah too, but it's slight in my eyes. Texas was a surprise to me. Just running sub 11 100 m isn't good enough to compete at State. Winners run around 10.4 100 m, and it's often tight between 5 with the numbers increasing drastically for every .1 second you go up in 100 m.
I think kids in Utah however are better prepared for college, make better use of their network, and have greater fortitude and success traveling out of state for college per capita.
Why'd I make such a long response singling you, you ask? I guess because I have the time and have finally gathered enough visual evidence for myself to formulate an educated opinion on the matter. My biggest flaw in sharing this info is first that it's my opinion and second that it's been 5 years since I've seen any Utah HS football in person. Cheerio:)