In general, you schedule games years in advance, so you can't time it to when a team is good or bad (although we have a knack for getting teams when they're down under Stoops...perhaps we should schedule tOSU so that we can crush their future), so you have to base it off of the overall outlook. Tulsa, in general, is a very good "mid-major" program, so I don't see why we wouldn't schedule them. We don't want to start our season off with a power-conference team, or even a team of BYU's caliber. You have to ease into it, or you'll end up shooting yourself in the foot once every 2-3 years. Tulsa is a team that we'll beat 19 times out of 20, yet they still have potential to add to our SOS.
Additionally, it's a very cost-effective "road-trip," and it allows the Tulsa families an opportunity to get to a game a lot easier. We've recruited decently in Tulsa, but we've let quite a few slip away over the years, and I have a hunch that if we played in Tulsa more often it would help us seal the deal on some of these guys.
Lastly, we're helping Tulsa by scheduling them, and helping Tulsa helps Oklahoma HS football, and by helping OK HS football we're helping ourselves.
In conclusion, I can't think of any reason NOT to schedule Tulsa. They shouldn't headline our non-conference, but Tulsa is usually our #2 opponent behind a Power-5 team, and that's teh way I think it should be.