Very different resorts. Wailea Marriott is one of the lower end hotels in the middle of the "Beverly Hills" section of Maui. It was bought out by Marriott from the Outrigger chain, and has a different feel (lots of low-rise buildings scattered on a pretty large campus) than other Marriotts. It's ocean front, but not beach front as there is no sandy beach directly in front of the resort. (You can walk to beaches on either side, though). You can stroll to other resorts and restaurants along an ocean front path, but you might end up feeling like you're staying at the Motel 6 in comparison, because the other resorts (Fairmont, Four Seasons, Grand Wailea) are the type that draws wealthy businessmen, not to mention the occasional celebrity.
Kapalua Ritz is a luxurious, self-contained resort off the beaten path. You're secluded enough that you might be tempted to eat most meals on site. You won't get to anyplace, including restaurants and night life, without getting in your car and heading south. Also, it's a 10-15 minute walk to the beach, though the beach itself is fabulous. Kapalua is reportedly windier and rainier than either Ka'anapali or Wailea, though I can't say I've noticed much of a difference when I've gone.
So, I'll throw the question back to you. What appeals to you more? A swanky hotel or a middle-of-the-road hotel in a swanky location?