I think Spurs fans are overrating Scola and underrating Oberto. I've seen a lot of Argentine basketball and I've always been on record that Oberto is as good a prospect to come in and contribute right away. Oberto is bigger, a better rebounder, a better defender, a better shotblocker and a better passer. In fact, Oberto is one of the best bigman passers I've ever seen.
Scola is good too, but he's overrated worldwide. He has a much higher ceiling than Oberto ... although I believe that he could bust in the NBA. Oberto, on the other hand, is what he is. He's basically a poor man's Vlade Divac who brings some of the same Manu-like toughness and hardnosed play to the court.
I like this move a lot. If it came down to Oberto for three-years at $4-6M and Scola for three-years at $10-12M ... this is what I would have done too. Oberto is an above average backup center in the league.
Now, this also gives the Spurs a lot of flexibility.
1) Trading Rasho. With three capable centers on the roster, Rasho can be traded. It wouldn't have made as much sense to trade him without bringing in another center.
2) Trading Scola. I know this would be an unpopular move, but the Spurs have to look at it. He's a little overvalued around the league right now and teams may be willing to give up a lot for him. There's also some question regarding when he buyout ends. I'm hearing that he might have TWO years remaining on his Spanish contract and the buyout is getting bigger by the year. If that's the case, trading him for a young prospect at a forward or guard position makes even more sense.
3) Using the MLE. I'm guessing Oberto is being signed with the LLE. If that is the case, now the full MLE is free to use. If the Spurs have someone in mind, that meant they couldn't really bring over Scola anyways and this signing helped strengthen their big positions.