I must ask a question to answer your question. Upon which island are you staying? If you have a choice I recommend Kauai. If you are staying on Oahu, I would recommend Ko’Olina vise Waikiki. Is this your first time to Hawaii? Then Waikiki may be the right answer because you will be in the middle of tourist center; however, once you've made the rounds in Waikiki, you will love being at the tranquil Ko’Olina. Please find my review of Kauai and look at the photo of the pool... The only other thing to keep in mind is the time of the year; January is viewed as being cold to Hawaiians (low 70's).
It really depends on switch island you will be visiting. I have stayed in Waikki beach but not at the Marriott -- its not favorite location. I love the island of Kauai - its quieter and slower paced. I have stayed at both the Kauai Beach Club and the Waiohai Beach Club. Both are wonderful properties - while the Kauai Beach Club has bigger beach and more centrally located on the island Waiohai has a great full size kitchen in the vacation club rooms. I'd recommend you decide what you want from a vacation and start with there. Either one of these properties in my opinion are great. In fact, we are returning for the third year this September.
We recently stayed 6 nights in Oahu at the Marriott Ko'olina and it was beautiful. The hotel is beautiful with great pools and beach. If you want to get away from the hustle and bustle of it all, this is the place. Do not stay in Waikiki if you want relaxation. It is way too crowded. Good luck!
I would recommend Kauai...it's less hectic than Oahu and easier to get around than Maui. As mentioned by someone else, the Waiohai has the advantage of having a full kitchen and washer/dryer in each unit; however, if your priorities on a vacation don't include cooking and cleaning, the Kauai Beach Club in Lihue is prettier, more resort-like, and has the added advantage of having the best Calamari (Duke's) I've ever had.
Please remember that Winter is the RAINY season. Summers are crowded and Spring/Fall is the best. On Kauai the Marriott Beach Club has a really large pool that is beautiful and they have good restaurants on site including Kukui's, Duke's and Cafe Portofino. On Maui the Marriott there is great and on the big island Hawaii the Waikaloa is right on a relly nice beach for activities. On Oahu the KoOlina is remote but beatiful and the Waikiki Marriott convenient to the beach.
My favorite Marriott hotel in Hawaii is the J.W. Marriott Ihilani in Ko'Olina on Oahu. It's not a very long drive to Waikiki (provided you're not driving during high-traffic times) and it is so much more peaceful than Waikiki. I've also stayed at the Marriott Beach Club on Kauai on their pool is amazing. They just finished a remodel there as well. I would recommend both properties. Enjoy Hawaii!