Having owned a large stack of Naim equipment as my last system, I have to acknowledge my opinion is somewhat biased, but for what it is worth, I did audition both the Supernait 3, the Hegel 190 and the Hegel 320 late last year and have some thoughts on them as follows:
I much preferred the Hegel integrateds to the Supernait but it's very much a stylistic preference. I'm not sure either is objectively or measurably better.
The Supernait is JANA - just another Naim amp - where all Naim amps do the same thing but to a greater degree the more you spend. So, great leading edge dynamics, effortless transients and reasonable detail but with the tendency to make your ears bleed and sound 'ugly' and harsh, especially the higher up you go (I experienced this - a good friend got as far as a ND555, 2x 555PS, NAC252 and active S600s driven by SNAXO and NAP300s before he finally bled out. He chopped it all in and has built a vastly different sytem. When I heard his final Naim set up I didn't have the heart to tell him it sounded utterly ghastly. Fortunately he reached that decision for himself.
But a lot of people like it (and at one time so did I) and as correctly pointed out, you rarely lose much money when you do finally bleed out and decide to take a different direction. It's also possible to get hefty discounts on Naim kit as the way Naim require their dealers to operate means they always have rotation demo stock they need to off load.
The Hegel amps in comparrison sound very musical; fluid, detailed and engaging. They had enough PRAT to be hugely entertaining but leading edfges weren't quite so brutal and the experience much more relaxing as a result. They were very similar to the T&A integrateds I also listened to at the same time, which were similarly impressive.