While Fitzgerald seems like a very strong "change of scenery" candidate, he did have a massively disappointing 2012 season (he almost single handedly killed my season in fantasy football), and he turns 30 just before the season opener next season. Sure, his QBs sucked, but they sucked in 2011 and he put up 1400 yards. I think there is some real upside but also some real risk with Fitz.
More importantly, he's inked to a massive contract that pays him until his age 36 season. The remainder of that deal is $103.25 million with roughly $25.5 million still guaranteed. His cap hit numbers
EXPLODE in 2014 and beyond, which is exactly when Seattle needs that money the most. His contract is a dealbreaker, IMO.
Surprisingly, Suh's numbers are just as bad. His cap hits over the next three years: $17.15m, $17.57m, $9.40m. It's unclear but I think his 2015 ($9.40m) year might be an "option" year or something because it wasn't reported on his initial contract signing. Suh is a great player and could be a missing piece, but you'd have to make a lot of sacrifices to keep his contract on the books for 2014.
Of the two, I'd prefer Suh. Not only is he a younger player at a bigger position of need, but at least Seattle could potentially work around his contract by trading Flynn and restructuring Miller (and fully utilizing all the RFA options Seattle has in 2014).
That said, dealing for Suh would be such a headache that I'd be just fine with avoiding it. And I also seriously doubt that Detroit would part with Suh for a single late 1st round pick. He would be an amazing player and an amazing story (local guy, sort of), but right now I don't see it. Maybe when he hits FA in 2016.