Here is just another example of usefulness of RAW. It seems that JPEG NR combined with long shutter NR is a real "detail killing" combo. I would definitely suggest to use RAW for long shutters.
See these crops:
As far as I remember, there was a discussion (somewhere on dpreview) about GRD detail smearing if using long shutters. I will try to test both cameras. But I think I already know the result
There will be visible some "hot pixels" in RAW (which are eliminated in JPEG), but these long shutter CCD artifacts can effectively be cleaned in any good RAW processor. For example, Silkypix does an excellent job in this area. And even if your RAW processor cannot handle the hot pixels, you can always do a dark frame subtraction in any "reasonable" image editor
Full res. Fine JPEG:
Full res. "DNG to JPEG" converted with SilkyPix (very conservative processing):