Personally I find that the 4000 is a perfect size. I use my symetry for every type of fishing. I use it for trout, steelhead, salmon, bass, etc. If I tried to do this with the 2000, I think I would end up replacing the line too often. With the 4000 it can hold enough line, to afford cutting off a long length of line without being affected. My opinion is to go with the 4000 just because it is my only reel. I really like this real and am thinking about getting another one. Just remember that your choice should be based upon your needs, and you shouldn't go wrong. Happy Hunting.
-Matt