Pegues probably isn't a good one to take advice from, but that decision is really a case by case basis.
Looking at our past players, both Oher and Willis were smart to come back. Both had room to up their draft stock and did.
Snead, on the other hand, should've gone after his redshirt sophomore year.
A lot depends on what you have coming back around you, your draft position, whether you have parts of your game that have room for dramatic improvement. If there isn't a ton of room for you to improve your draft stock, whether due to being near your own personal ceiling or being near the top of the draft, you go because you only have so many years to play. To come back, you have to be able to justify that you're going to make up for that year of lost revenue by getting a significantly higher signing bonus in the following draft.
That's why Andrew Luck was dumb last year in a pure athletic career sense. You can't get higher than the No. 1 pick. All he did was play one more year for free that he won't get back on the back end of his career.
I can't remember if Anthony Dixon had the opportunity to leave early, but he definitely helped himself a lot by coming back, losing weight, and becoming a better receiver out of the backfield. He went from likely an undrafted free agent that may not have made a team to a draft pick that did make a team with a decent contract.