If your light and dark frames on the 383L+ need scaling, then it sounds like the unit is defective. Any CCD with setpoint cooling should be keeping the temperature within a 1 degree range, and usually it's within a 0.1 degree range. A one degree fluctuation is too small to matter for dark subtraction...if your needing scaling, then temps must be differing by several degrees, in which case, your regulation is failing, resulting in oscillating temperatures. Atik should be able to fix that if the unit is under warranty.
As for Iris, good that it uses noise evaluation.
As for PixInsight, PI does not on it's own produce an intrinsic "look" for images processed with it. How your images look when processed with PI is 100% all up to the user. If you didn't like the look of your images, then you didn't like the look of your own processing. ;P
PI takes time to learn. It is significantly more powerful and capable than Iris, and if you give yourself some time to learn it, you can produce significantly better images with it. However, you have to give yourself some time with the program. It took me about six months to learn PI well enough to start producing images I really liked with it. A lot of that was learning how to use previews, the rest was learning how to generate the right kind of masks to use in concert with various tools. Masking is a critical part of successful PI processing.
One of the most common beginner mistakes with PI is to perform noise reduction with insufficient masking, and to use the NR tools in the wrong way or in the wrong order. TGVDenoise is a powerful NR tool, but it is very easy to totally obliterate high frequency noise, leaving behind lower frequencies of noise...that often results in the dreaded "orange skin" look to your background sky. The solution to that is to heavily mask TGV, which attenuates it's effect. You still get a light orange skin, but you don't obliterate the high frequency noise, which makes another tool, MMT (Multiscale Median Transform) work very well to clean up the orange skinning. Again, though, MMT needs to be heavily attenuated, and run with very high settings, to actually work properly.
PI can produce amazing results. Just take a look at my more recent images here:
http://www.astrobin.com/users/jrista/
My two most recent galaxy images used proper NR techniques, and they look significantly better than some of my earlier attempts, which do not use proper NR techniques. Compare my M101 with my M51...namely the background sky. In M101, which I processed early January, when I didn't quite have a handle on proper masking, the orange skinning effect in the background is apparent. In M51, I had a much better handle on masking, and I was able to properly attenuate NR and get a smooth, clean background sky.
PI can be used to great effect, but you do have to give yourself the proper chance to learn it.