Exactly. I like advanced stats too, but this is a perfect example of why they're not everything. Spurs fans adhere to that when it's a player they're nostalgic about, like Jackson, but when it's a player they don't care about on a team they don't care about, suddenly advanced stats are the be all end all. The difference between Randolph and Davis is, Randolph can be an offensive centerpiece type. Davis, on the other hand, is and always will be an ancillary scorer. You're bang on with your assessment of him.
They can have all the financial flexibility they want, the bottom line is, for the reasons I've already stated, they'll be hard pressed to build a team as good as the one they had, let alone better. A Gasol, Conley, Davis core isn't great and I don't think they'll get a massive piece for Randolph, either.
As for the Pistons, this is an outstanding move. They clear long term salary, get a quality, play making PG and a guy who could make Drummond an even more serious threat in the pick-and-roll, while eliminating their logjam at SF.