The towers are very similar. Waianae tower is a bit smaller, closer to the adult pool, spa, parking garage, and Ulu Café. Ewa tower has the store, closer to Aunty's, Off the Hook, Ama Ama, and the lawn where the luau is located. Both towers are connected at floor 3 where the lobby is. I wouldn't consider Aulani a massive or sprawling resort, so its easy to get between the two. IMO, one doesn't have a larger advantage over the other.
We had a standard studio and made no room requests. We were on floor 5 in Ewa tower and our room overlooked the courtyard of the convention space. We saw a wedding take place there and some high profile politicians give speeches. It was cool to have that vantage point, but the room didn't have a lot of natural light. I'm not sure what room category overlooks the luau lawn in Ewa, but that might be a cool room to have. I'm thinking standard view in Waianae tower would likely face the Four Seasons or possibly the parking structure/front driveway.
I'm not sure whether there are standard rooms on the ground floor, I would assume so, but I'd caution against noise with ground floor rooms. The pathways are narrow and I remember walking past the pool facing ground floor rooms and thinking it would be annoying with all the foot traffic going by. The only advantage is that you can essentially walk out your patio and you're in the pool complex, but I don't imagine these rooms are considered standard. Also, keep in mind that the lobby and store are on floor 3, so you'd be going up to get to those spots.
