We have also stayed at Kaanapali, and now we choose Wailea every time. It's our favorite beach (probably in the world). The Marriott had a great spa facility if you're looking for any of those services as well.

A couple of caveats:

As cougarfann888 mentioned, you have to walk a little way off the property to get to Wailea beach. The actual beachfront properties are the Waldorf Astoria, The Ritz, and a few other high-end resorts. The Marriott is next to the Waldorf.

If you're looking for more of a 'city' close by, then Kaanapali is close to Lahaina which has more to do. But when we go to Maui, we want to hit the beach most of the time and then a few other adventures. Since the beach is our priority, we go with Wailea.