I have owned both the PS3 Move, and the Xbox Kinect. The Move, took more time to set up and calibrate, than the time that I actually spent using it. Move, felt like a "Glorified" version of the Wii (and at the time, it basically cost me as much as a Wii system for two people to play). Kinect, was easy to set up, and out-of-the-box supports 4 players at the same time. I actually use the Kinect almost everyday. The most useful feature for me, is the voice recognition. I control entire dashboard of the system by voice, and control playback for movies (in Zune, Netflix etc.) on a daily basis.
If you own a Kinect, do yourself a favor and spend $10 on Fruit Ninja.
Go for Kinect, you won't be sorry. I have it and it's simply awesome. I tried the PS3 just to make sure but the kinect is much cooler and easier to use. Go ahead and do the upgrade, I assure you you'll be happy you did