They SHOULD both be good to go as far as authenticity and "what the players wear." Each team does have a few variations though, and may change slightly from year to year.
IMO, if you get something from a reliable seller (ie. MLB.com or Majestic, etc) then it should be the goods. If it's an MLB jersey made by Majestic, then it should be authentic, be it a replica or a real, in which case it should be clearly noted somewhere.
[quote:4fef447375="Geek"]The odds of the AL MVP coming from the American League are looking pretty good.[/quote]