Rebel XTi upgrade choices
I've had my dear old Rebel XTi for about 4 years now. I've had good times with the camera, but with the number of available features on the 7D (especially the expanded ISO and the video capability) I'm considering upgrading. However, once I looked into it, I realized that the 50D had gotten considerably cheaper and I now have a dilemma.
What originally pushed me to get a SLR was to shoot in low light without a flash, and those photos are still the ones I like best. Movies are nice, but not a big deal.
I'm mostly shooting with just-above-basic-lenses (just got a canon 50mm 1.4), as L lenses are beyond my capabilities. How much better (if at all) is the low-light aspect of the 7D over the 50D? To people who've had both, what stands out about the 7D over the 50D? Given that I'm coming from the Rebel - is the 7D worth the extra $600 or so (new)?