Looks like you missed the part about poise and being a better outside shooting weapon, as well as seeing both players prior to their arrival at their current school.
Unless things change - this is a no brainer. Hollins is younger with a higher upside and quickness. If the competition is close, you have to go with Hollins in the hope that his development curve brings the whole team up a notch by the end of the year. Last game Tubby had Welch playing at the 2 guard most of the time as Ahanmisi is now the PG backup. Things could change, I like a lot of things about Welch, he's got quick hands and long arms on defense and it looks like he can shoot. We may see him used in a lot of ways - sometimes at the 2 with a smaller lineup that moves Hollins to the 3 or perhaps at the point in big lineup.