I'm not familiar with the Andaz, but we stayed at the Westin Maui and loved it! My trip report is in my signature.
We did not have a rental car while on Maui so for us, the Westin was the perfect location. The side door of the Westin is literally steps to Whaler's Village, so it was nice to walk there in the evening for shopping and dining/drinks. The Starwood resorts in that area (Westin, Westin Villas, Sheraton) all run a free shuttle that loops between the resorts, Cannery Mall, the outlets, and Lahaina. It runs on a good schedule and was very convenient for us to go down to Lahaina (we loved that area!).
The Westin itself was beautiful and probably my favorite of the resorts we stayed at while in Hawaii, not including Aulani. The Westin was the smallest of the resorts we stayed in, but that made it feel not so crowded and was easy to navigate. The pool was amazing and all the food we had there was good too. Our room was upgraded from mountain view to partial ocean view and was on floor 4, right above Whaler's Village, but we never heard it. Friends of ours had a destination wedding there back in October, and they loved it as well.