A 5 seed vs a 9 seed would be not too different. Latest bracketology example: Marquette(5) and Oklahoma(9); Arizona (5) and Florida (9), Colorado(5) and St. Mary's(9), Oregon(5) and Rhode Island (9).

As you can see... rd 1 opponent whether a 5 or a 9 is fairly similar. HOWEVER, if you win that game... the next round as a 12 seed you would face either a 4 or 13 seed. If you were an 8 seed you face a 1 seed. 

So ask yourself, in round 2 would you rather play Duke, Baylor, Kansas... or Crieghton, Villanova, Auburn?

That is why a 12 is better than an 8.

I think BYU can beat Creighton, Villanova and Auburn... however, it would be difficult to beat Kansas (already lost), Duke or Baylor with 1 day of prep.