I just shipped out a new PSR2100 today to Joe Waters of PSRTutorial. If you don't know about Joe's site, he has developed a web site dedicated to using the PSR2000 and it has developed also into Tyros help as well, and now, with Joe owning a PSR2100 he would be a great one to do a side by side comparison in detail for you.
Also, Yamaha has PSR2100 keyboards available in stock as of today. I have sold all of my first shipment as of 5PM today and I called and ordered more from Yamaha and they are in stock in Buena Park, California.
George Kaye
Kaye's Music Scene
Reseda, California