Canon Eos 50d Digital

Canon 450D Canon 500D VS What ??!!?
Okay, so I'm in the market for a digital SLR and I compared the Canon EOS Digital Rebel XSI for Canon EOS 50D and 50D is just better, and I mean barely! can you record HD video and why! Both devices have the same sensor! the 50D is just better with little light XSI, but has a faster shutter speed. Anyway, the XSI is priced at $ 650 with kit lens and the 50D is priced at $ 1,200 with a lens kit and I think why the hell should I spend almost twice as much for a 50D?? no sense! Can someone help me with that? I prefer photographers and people experienced in using both chambers reply please, thanks.
They do not have the same sensor … different microprocessors. Compare the cameras here … http://www.canon.co.uk/for_home/compare_products/LoadComparator.asp
Unboxing the Canon EOS 50D and 18-55 IS