I honestly don't think you can lose with any of these guys. The floor for all of them is pretty high. But if you want to look at ceiling...
Julio has by far the highest ceiling. I'm lucky enough to have him as a keeper in a PPR league in the late 3rd round, I'm sure he would've been gone by early 2nd otherwise. Don't kid yourself, ADP for Julio is stupidly low - by the start of the season he'll be going early 2nd.
I'd be going Welker second only because he has the highest floor of all of these guys. Bringing in Lloyd isn't going to hurt him, it'll help. Spreading the defense means more room in the middle - Welker is going to run wild again this year. The only reason I have him below Julio is because his TD total is going to be lower.
AJ and Marshall are a crapshoot. AJ may be slowed down a bit by not having any other receivers to draw coverage, meaning he'll be double teamed all day. Marshall and Cutler could easily go off like they have in the past, but they're both a little older - we'll see if either have lost a step. Even if they haven't, there's no guarantee the magic is still there. I still like Marshall for 80-1000-8 though, about the same as AJ. Maybe a bit higher on the yardage total for AJ (1100 let's say), but I think he'll be a bit lower on receptions (70-75) just because of coverage.