Reality is that you should be focusing via the camera USB to a laptop screen....purely for the resolution and ability to use control/capture and focusing software like
APT or
BYE.
You can use the rear LCD but it's just too damn hard and gets into hard to see places as the scope moves and press the LCD enlarge buttons. Much easier to do this via software.
I would get the
600D purely from it's lower noise perspective. That said...the
1100D isn't a bad camera at all.
Either camera is good!
edit:
The winner is...1100D...
$299 cheapest price (body only)