Although no doubt the D3200 is a great camera (I had a D3100), I think coming from the D300 you may find the AF system/control and the viewfinder rather difficult to adjust to. The D7000 is a great camera and is comparatively light and compact, plus it has great AF and an excellent viewfinder.
Obviously there is a ton of other differences, but I personally have found those two mentioned above the most frustrating on entry level bodies. IQ will be excellent on both of course.