Can't help you on this, since we like both places. I like the Biergarten too, but DW is not so keen on it. We are debating between San Angel and Marrakesh for October, as we like both quite a bit. I like the atmosphere at Marrakesh, with the music and belly dancer; very entertaining. Frankly, they serve better Moroccan food at Spoodles on the Boardwalk or Jiko at AKL, but the food is still pretty good. On the other hand, San Angel is a wonderful quiet and dark oasis on a hot steamy Florida day. You watch the boats on the Rio del Tiempo ride disappear into the ride (kinda hokey, but fun - one of 5 yr old DD's favorites). The food is upscale Mexican, not Tex-Mex that we're all used to. There are baskets of tortilla chips on the table, but the food is better than many "Mexican" restaurants un North America. We like it for the atmosphere, and the kids enjoy it. I'd take the Biergarten any day, but DW would prefer San Angel or Marrakesh.
Good luck with the decision.