Manning is currently in US military custody and on trial for leaking about a half a million classified documents to Wikileaks. Snowden leaked to the Guardian newspaper details of various intelligence gathering programs and is currently stuck in a transit area of Sheremetevo, one of Moscow's three international airports.
So what is the big difference between the two?
Well one is slightly more at liberty than the other but the big difference is that Manning had SECRET clearance while Snowden had TOP SECRET clearance. Both have stashed encrypted DVDs containing stolen documents yet to be made public, but Snowden's "insurance policy" is likely to be far more effective than Manning's.
Manning had quantity and Snowden has quality.