Both pictures was exposed using the same setup – GSO 150 f/5 newtonian scope. It is quite fortunate that both Canon 20D and Atik 314L+ have similar pixel size, so the image scale is about the same. However please keep in mind, that Canon camera has RGGB Bayer matrix (Atik is monochrome camera) and also IR filter, so it is less sensitive to the red light (especially with regards to H alpha emission line). Bayer matrix also means a little bit worse spatial resolution. Additionally more thermal noise is present for DSLR camera (comparing to thermoelectrically cooled Atik camera), but also light pollution noise has some significant effect especially under suburb sky with limiting magnitude about 5mag.
Nevertheless the conclusion is fairly simple – DSLR astrophotography was real fun and gave me great opportunity to get into deep space astrophotography with decent bang for a buck ratio. “Real” CCD astro camera on the other hand even under suburb night sky gives us brand new picture quality of our precious sky targets. However it comes at a price of new problems to fight with – especially for monochrome camera with color filter set.