Lot of anti-BJJ bias running around.
Greco is not going to teach you groundfighting in any appreciable way. You will learn a lot of throws and upper body clinch skills. The touch/exposure fall of Greco limits groundgrappling in a way that makes it ill suited for combat ON THE GROUND. It has other highlights, but that’s not one of them. Folkstyle wrestling, frequently called collegiate or scholastic in the U.S. has a heavy emphasis on controlling the opponent on the mat. Consequently, there is a higher degree of matwork. In fact, the majority of the match takes place on the mat. Usually. 
Catch wrestling is ummm… well, the honest truth is that, not only are hookers few and far between, nobody can really decide what Catch means. It’s a DEAD ART, like latin is a dead language. You can try and recreate it, you can even read and write it, but nobody REALLY KNOWS FOR CERTAIN what this was. We have books and photos and some really good ideas about what all this is, but the line between Catch and early “WWF,” type matches is so blurry I don’t think anybody really knows where one stopped and the other began. I’m not knocking catch, I’m just trying to throw some historical perspective on things. It’s basically wrestling with Submissions, and it carries over wrestling’s aggressive physicality along with a knack for slapping hooks (submissions) in in some places other arts might find very odd. It’s good stuff, but finding “real,” Catch isn’t going to be easy–and they have more lineage type arguments than WC. Good BJJ feels like a straight jacket made of water. Good Catch Wrestlers feel like they are trying to mug you. Both work fine. The guard is heavily de-emphasized in Catch. That’s not necessarily a bad thing, but it poses it’s own set of problems.
Judo does have a lot of the BJJ groundwork. However, the argument that these two are one and the same holds no water for me. They have diverged sufficiently to become seperate entities, IMO. In Judo you will at least learn the rudiments of groundfighting, but there is no guarentee you will spend much time on the mat. Very generally speaking, a person who has spent 2 years in BJJ will wipe the mat with a 2 year Judoka, IF you limit the discussion to groundwork only. Stand-up, and watch the BJJer’s feet hit the ceiling as he gets thrown like a ragdoll :). It’s a matter of what you train. Judo’s emphasis, for the most part, and as it is commonly taught, is about the throw. Again, not a bad thing. But groundwork focused per se? No.
Sambo will expose you to a greater variety of locks. Neat stuff. The rules of Sportive Sambo limit groundwork time to some extent, so there is a “bang away,” feeling for the submission. Be prepared to garner some major leg injuries if you do this stuff. I’ve never met a Sambo player who didn’t hurt their knee severely at least once. Sambo guys tend to be vulnerable to a good guard player because it’s not used very often. On the other hand, BJJ guys frequently fall prey to Sambo’s leg-lock expertise. Six of one, have dozen of the other.
Most BJJ schools have at least one class a week of no gi work. Most of your BJJ moves will work without the gi. They are just modified slightly and the setups change a little.
