Gallandro, I have bowled some on the Sport patterns (although not regularly), and I can indeed see where urethane might be a very worthwhile option on the Sport conditions.  Urethane isn't nearly as prone to the over/under reaction that you would see with reactive resin or particle balls on the Sport pattern, so urethane does make sense.  At least trying urethane on the Sport patterns would be worth a try, and I would speculate that it might prove to be a good idea.  A dull urethane ball sounds like a good idea to me!....at least it won't hurt to try.

Depending on the amount of oil in your sport league, a solid or a pearl urethane can be a very good idea. I finished up my last 3 frames last week going up the 5 board (OK, make that trying to go up the 5 board) with my pearl urethane. I should have tried that much earlier in the night!

However, on 99% of all sport shots, I would have to believe one is not going to "open up the shot" with any ball. Control balls are what you want, whether the shot is oily or dry-ish, you want a small hook because the sport shots are or should be designed to limit the typical wide open house shot. One normally has 1-3 boards of area, vs the normal house shot of 6-10 boards of area.