Canon EOS Digital Rebel XT vs. Pentax *ist DL SLR Digital

Long story short, I am looking to upgrade from my Canon Powershot to an SLR and was recommended these two for my price range by a local camera shop. He didn't have the biggest selection but he came as the only recommended camera shop within a 40mile radius. I would like to buy locally from him unless I can get either one for a lot cheaper by going online or something retail. The Canon is $1020 for the body, 18-55mm lens, and 75-300mm lens whereas the Pentax is $700 for the same. I will mostly be using the camera for general purpose shooting... night shots of stars and such, time-lapse for minutes or maybe hours, sunsets/rises, ducks on a lake, people, action shots of nephews playing soccer, etc. Can anyone tell me if these cameras will do the job or if I should be looking elsewhere? Also, is the Canon worth the extra? Thanks for all of the help I know I will recieve.