It's impossible to even compare Key West and SoWal. I like both SoWal and Key West, but for entirely different reasons. Key West is a great place if you want to party 24/7, be loud, get drunk, run into a bunch of drunks and strange people who you'll probably never see again (thankfully!), etc., while SoWal is a place to RELAX, enjoy the beautiful white sandy beaches, enjoy the nature walks and bike trails, great food, meet neat people who you'll probably run into again on another trip down to SoWal, etc. SoWal has the best beaches anywhere; Key West beaches absolutely suck....they're the worst, and not even pretty. Duvall Street, Key West's "party street" is dirty, smells like throw-up and you pretty much have to watch where you're walking so you don't trip over the drunks. Nothing like the beauty of walking along 30-A, where you can smell and hear the ocean, exchange smiles and "hello's" with fellow bicyclers and walkers.
Key West has a lot of history...Hemingway, lighthouse, etc.....and the Key Lime Shoppe serves up the yummiest chocolate covered key lime pie on a stick. There are things to do other than party. But my disappointment the first time I visited Key West 14 years ago was how commercialized it was; I expected a tropical paradise, and it was nothing like that. It's definitely an "anything goes" place, and it's fun for a very short duration, but it is certainly not deserving of being compared to the beauty and ambviance of SoWal!