Ok, I'm not sure where I should put this... but I thought this might be a good place. Say I'm shooting an engagement session in which I have time between my shots. and say I have a 40d and a rebel XT, along with a fast 18-50 and a fast 70-200... With this in mind, would it be better to use just the 40d and swap the lenses back and forth as needed? or would it be better to to put say the more used lens on the 40d and the lesser used lens on the XT? The reason I ask is that I hate to switch lenses, but then again, the difference in quality between the XT and the 40d is obviously a fair amount. What is your opinion?