Aramis is a good hitter, but he's also a below average defender with some significant health issues. I don't know much about Weaver, but if he's really a top of the rotation starter he would probably be worth more to the team than Ramirez. FYI, in Aramis' best season, his WARP3 was 6.3. Carlos Zambrano, by way of comparison, has been worth 7.9, 8.8 and 7.8.