We have stayed at Aulani three times and have been in three different parts of the resort. All three times we were in studios: once in a Pool View villa (Waianae Building villa #304); once in an Ocean View villa (Ewa Phase 1 Building villa #1154); and once in an Ocean View villa (Ewa Phase 3 Building villa #1578).
The parking garage is on the Waianae side of the resort so those villas are a bit easier to access if you have a car. Aulani is fairly compact, so its easy to get to almost any part of the resort from any room.
If given a choice, I prefer the villas in the Ewa Phase 3 Long Wing, which are villas xx70 - xx89. The villas facing the Waikolohe Valley offer shade in the morning and afternoon sun, as well as at least partial views of the sunset. The Waianae Building villas xx01 - xx12 facing the Waikolohe Valley offer morning sun and afternoon shade. They would be my second choice when booking an Ocean View Villa.
When choosing a location, some people consider whether the villa has an angled balcony or a straight, non angled balcony. Except for the Grand Villas, the Waianae Building DVC villas (xx02 - xx13) and the Ewa Phase 3 Long Wing (xx70- xx88) have angled balconies. The Ewa Phase 1 Building (xx50 - xx59) and the Ewa Phase 3 Building Short Wing (xx60 - xx69) have straight non angled balconies.
I prefer the Studios with angled balconies because the room configuration is slightly different. The studios with angled balconies have two nightstands, one on each side of the bed. The studios with the non angled balconies have only one nightstand.