Been going to both for years, Oshkosh is a class act and well managed. Only downside to me for airventure is the lack of normal hotels coupled with occasional excessively hot weather. Been there about 20+ times, aircraft camping, RV camping and dorm. Sun-N-Fun has had its issues over the years mostly after the show went over to local government and away from the EAA folks that were running it. There's been a significant downturn in attendance, vendors and fly in aircraft. Aircraft camping is only about 10% of what it was in its heyday. Thankfully the leadership changed a couple of years back and there's been improvements and a resurgence. Still worth attending and there are some really nice people there. RV camping is both nice and close BUT they chase out 90% of the campers (aircraft and RV) whenever the military team of the year wishes to practice or has a show. I've tried to avoid the convention during those years as it's a major inconvenience.
Importance at airshows in order:
Socialization (people), aircraft (experimental, display, (real) warbirds, certifieds, (wannabee) warbirds, vendors, forums, events, airshow, conveniences (weather, grounds, accomodations, etc)
I attended SnF in 2012/13. Both years we were there when the gates opened, and both years were done by 1:30.
I went mostly for homebuilts and the exhibits. Really don't care to count rivets on warbirds. I respect them, but more like Clark W Griswold looking at the Grand Canyon.
Had more fun at Kermit Weeks' place.
Yes, Sun N Fun is not as big and exciting as Oshkosh, but I still have a great time there. It is the second best fly-in airshow that I know of. I flew down on Thursday this year and camped by my plane thru Sunday morning. My biggest complaint is the food service. By the time I left on Sunday, I was ready to get home to some good food again. Otherwise, there was plenty to do to keep my interest for that time span.
One of the earlier posters said it doesn't get cold there. It is not cold like you experience in the North, but Saturday night was pretty chilly during the night airshow. It was too cold out for a light wind breaker, although I was reasonably comfortable in my tent and sleeping bag.