i would do classic until the next retail expansion. in the next expansion after you level one character(team) to max level..there are going to be better options for any alts after that. As well as, after level 10, you can choose any of the past expansion zones to level alt teams in all the way to 50 ( 50 to 60 will be in the new expansion zones ). This way you will experience all classic has to offer, and if you want, you can experience any of the past expansions in retail, in any order you want, ( after first character/team hits max level.)