some people here have a hard time believing that anything but their own boat brand has the capability to float for more than a few years in flat water.
I have an NRS E-Series, and think it is as well made as any other. like anything, there are different grades of boats in the NRS lineup- the cat tubes are basically otter quality (used to be about 36oz, now is 41 oz's of hypalon on 1100 denier base fabric, where the E-series is 48oz on 1670 denier fabric) The boats bottom is 3-5 layers thick is most places. I have been nothing but impressed with my boat.
I had 3 different hysides, (pro, outfitter, and rio bravo) and they were all good boats. if you actually want answers about the differences, I would call Mark or Judy at AAA- they sell RMR, Aire, Hyside, Achilles, Avon, and NRS. ask them (or any store that sells multiple brands that you are considering) what they like and why.
As for price, while the boat is the biggest part of the equation, you will be spending lots more, and a couple hundy one way or the other will vanish quickly, in the whole scheme of things. get what you like and get it wet alot.