I'll play Devil's Advocate and say take Roy Williams, and here's why:
Those are some of Roy W's best games as a pro, and yes I know that some of these games are from 2006 and 2007, but I do know that I have seen Roy dominate at the NFL level before, and be a legit #1 WR before...Don't let me forget this was with Joey Harrington and no other WR's at all to draw away any coverage from him...In fact, Roy W had over 800 yards receiving his rookie year with Joey Harrington that year, Crabtree I highly doubt tops that coming from a spread offense and off of a surgery.
Now he's getting a real QB that actually has some accuracy, he has arguably the games best TE to draw coverage that he never had in Detroit, and he basically has the support of Jerry Jones who has all but said their going to make sure Roy gets his touches this year, if for anything to validate the trade in which he over payed.
Yes I know Crabtree is a freak, yes I know his college numbers were incredible, but he's far from a sure thing playing in that Texas Tech offense, and right now he's nothing but potential...I don't think he's the cant miss prospect Calvin Johnson was, and all that potential is alot to be riding on over a guy who is likely to get 80 catches, 1200 yards, and double digit TD's.
Roy did start to get lazy last year once he wasn't getting the ball, but with TO gone and in a pass-happy offensive system he's set up to have a huge bounce back year and be perfectly happy. Like I said even if it was a few years game there is alot of evidence that Roy can put up dominant stats and be a fantasy beast, as much as Garrett will be wanting to throw the ball he'll be more productive then Crabtree at least for the first two years and maybe more until SF turns into the passing team Dallas is.
Current Cafe Dynasties:
4th and Goal
Fourth & Inches
Any Given Dynasty
Eat Cheese Dynasty
Cafe Very Special Forces