Cahill - Minors 238ip- 6.2(H/9) 0.3(HR/9) 3.7(BB/9) 10.0(K/9)
Cahill 2009 Majors 126ip- 9.8(H/9) 1.8(HR/9) 3.9(BB/9) 4.6(K/9)
Snider - Minors 1288ab- .301/.380/.530 62HR 14SB
Snider 2009 AAA 150ab - .320/.417/.653 12HR 2SB 24BB 41K
Both are 21 and former top prospects. I have never really been a big fan of Cahill, so I may be biased, but I take Snider over him. I think it really comes down to what your team needs more, hitting or pitching. I think Cahill ends up being a #2, while Snider has the ability to be a .280 30HR 100RBI guy. I come from the camp that thinks hitters are "safer" than pitchers, so that also tips it in Sniders favor.
I would take Snider.