Both resorts used to be Starwood properties. I stayed at the Lodge in Feb 2008 and at Manele Bay in April 2009. As the other posters said, it completely depends on what you want in a vacation.
The Lodge is really unique. Depending on what time of year you're visiting, though, you may not get the heat/sun of Hawaii. In Feb and Apr, having visited the Lodge, I definitely wore jeans and a sweater. Sometimes there is fog. If you're looking for a romantic, beautiful place that is NOT the beach, then the Lodge really fits the bill. Gorgeous grounds (the landscaping is really spectacular, I was stunned). Activities like lawn bowling (with no one else around), croquet, executive putting, very easy and serene activities. The Lodge inside has a grand hall. Dark woods, fireplaces, a bar/oak room with drinks.
If you're going to Hawaii because of the beach and sun, Manele Bay is great. The rooms are nice (the Lodge actually has nicer rooms in my opinion). The pool is standard but nice, two hot tubs, and a pretty easy walk down to the beach. Service at the pool and beach is superb. Chair set up, food/drink service (at the pool).
Lodge is less expensive. Yes you can visit both resorts, but definitely stay longer at the one you want to be at.
Can you tell us something about the vacation you're trying to have? Maybe that would help...