Mict, I'm a big fan of the JW (see TR below) and have only stayed there so I can't give you much of a comparison perspective but I can tell you the Marriott properties are North of the airport and most (...all) of the 'action' is South.
If you want to do touristy stuff like Surin Beach, Patong, maybe a boat ride to Phi Phi look at properties a little further South.
My wife and I love the JW, it's perfect for us, but we're not into some of the "going out" or night life things. So depending on what you want the Marriott properties may not work for you as well - taxi's are cheap but they add up quick when you are 30+ min from everything.