Buy the new one. Stay away from rebuilt.
Usually rebuilt parts don't scare me but an AC compressor is a little different IMO for a couple of reasons. One, they are very very touchy to rebuild. They have delicate innards that don't like to be messed with. Two, if you buy a compressor and in a year it blows up you have to pay extra to have it recharged. It's not like you can just pull it off, take it back to the parts store, get a new one, slap it on and be on your way. You still have to deal with the other crap.