Most of this information on this webpage is focused on South/Central Maui.
If you are staying on Maui for a short amount of time and want to minimize wasted time, I strongly recommend you stay in Kihei, especially if you are younger (under 60) and/or have children.
The most touted activities on Maui (zip lining, horseback riding, Maalaea Ocean Center, Paia town, road to Hana, etc.) are more easily reached from south/central Maui than the westside of Lahaina.
If you stay in Lahaina, you are adding at least an hour’s driving time to every activity mentioned above. Of course, there are beautiful places to stay, horseback riding, etc. in the Lahaina area, but many visitors, especially those new to Maui, are drawn toward the east side of Maui due to the tales of the rainforest beauty of Keanae and its waterfalls, the mystical bamboo forest, the legendary road trip to Hana and the windsurfing capital of the world, Paia.
South or Central Maui is in between the west and east side, so you're at an advantage because you can travel the shorter distance to either side.
Lahaina is also beautiful for its own sites and tours but I think if you are only here "once in a lifetime", save Lahaina for a day trip.