Black and White would be a better option on my opinion. You don't need to rely on the Battle Frontier for moves. TMs are perfectly good, plus B/W have new moves such as Scald the do very nicely in movesets.
B/W also have lots of areas to train, like HG/SS, but in B/W I find it easier to find high leveled Pokemon, and Audino can be found at LV. 55 @ Giant Chasm.
It sorta depends on what Pokemon you are training cause' each game have differant Pokemon that offer better EVs that another, too.
Info on EVs: http://pokemondb.net/ev