The 146 wasn't even upgraded for PRNAV compliance retrospectively. THe RJ's had it from build, thought it was withdrawn for a while and then re-introduced when some technical solutions to altitude bursting were developed and introduced. I short there have been very few improvements but to gerneralise the RJ has EFIS, CAT III autoland, FADEC and 507 engines. THe 146 started with an elecromechanical flightdeck, had EFIS inroduced halfway through its life but no FADEC or CAT III and had 502 engines.