Except in 3.5's. They are the same strength once they get up to 3.5Java Reds are filed; this makes a difference for some players. The Reds are also a little more firm than the Greens in the same strength. For me, the Reds are a little more lively than the Greens, but some players have exactly the opposite experience. There's simply no substitution for purchasing a box (or two) of each, playing them for a while, then deciding which is best for you.
+1 Try the sample pack you might like the ZZ and V16 as well.Vandoren has sampler packs with Java Red, Java Green, ZZ and V16. You might want to pick up one of these. Of course it is hard to make a full evaluation with a sample size of one, but it will give you some idea how they play.