My friend and pitching coach was a first round draft pick, he told me it was a no brainer to take the money at that time, but a 3rd rounder or lower would be better off in college, usually, he speculated. I figure the better college players could step into AA ball and not miss a beat, the best could play AAA, and of course the top few could play MLB with some adjustment. My friend said the jump from AA to AAA was the steepest, the AAA players generally are ready for MLB level play, perhaps with some small deficiencies they work on.
Some of it is who is ahead of you at your position obviously.