I think they're both a bit overhyped. Weaver worked everything off the fastball in college. His curve is rated as pretty average. Jared, Jeff...I don't see a whole lot of difference to be honest. A big leaguer for sure, but I believe the #3 starter projections are probably pretty accurate.
Sizemore isn't doing much at AAA, and while he keeps on getting the rave reviews, I'm still not seeing the production. He's got speed, but the fact that he gets thrown out stealing close to half the time in the minors doesn't bode well for him being a big time SB guy in the show. His power has yet to show. I'm not saying he won't be productive in the majors, but I don't think it will be anywhere near as sensational as the prospect guides do. Remember, virtually all these publications have tendency to overhype to some extent. Sizemore could very well be a 20/20 with a decent average, but that's not elite. I'm thinking more like 20/15.
I'll rate Sizemore ahead of Weaver as I always prefer offense.