I would say go with the Ninja (oh I so wanted one of them 6 months ago). For all the reasons you mentioned plus
– you will get most (if not all) of your money back if you decide to upgrade later
– with this economy the price of those 600R’s is not going up anytime soon
I don’t know much (ok, anything) about the 600R so cannot comment on how beginner friendly that is but I think you are making a mistake about riding before your course. At least your reasons for it. The course is designed for beginners. I had never sat on a bike before the course and I passed. By teaching yourself beforehand you run the risk of
a) crashing your bike
b) learning yourself bad habits
I honestly think you would do more harm than good by learning beforehand. Plenty of time to build up those muscle habits afterward.