Custom roms generally are tweaked to be a bit more speedy, have the bloat taken out and allow you, the user, to do things that are usually not allowed or limited.
Don't ask what is the best rom as it is rude and will start a rom war. You need to go to the developement section, pick the roms that are compatible with your device, n8010/13 rom won't allow the n8000 to use its phone functions, and then read the posts.... Decide what you want then flash. The beauty is, as long as you do a nandroid backup, you can return to your stock rom or try another rom as many times as you want...