What do you think about this statement

>>What do you think about this statement<<

I'd say that's his opinion.

What's his favorite flavor of ice cream?

Since you met at a party why not meet again at each other's house and hear for yourselves' the difference?
The worst that can happen is two evenings of some wine(?), good music, and hopefully good company. Rather than go with other people's ears, here's a chance to use your own.
Listen and enjoy.

he has his opinion. the forums here have zillions. just do a search on the subject and you'll probably get a lot more ideas (opinions, but some more informed and well-articulated than others...) about the differences between these brands.

or, as has been said, you could actually listen to some Naim gear and decide if you like it enough to consider a home audition...

Uru got right to the point.

Good and bad are opposite sides of the same coin! It comes down to taste and system matching!

A Naim system does certain things very well and doesn't do other things. So it depends on what your friend finds pleasing! A Naim system has propulsive bass, a warm midrange, and is quite dynamic.

An ARC system depending on the setup will throw a much better sound stage, and will have depth to the image. However the bass and dynamics may not be as force full.

So it comes down to system matching and preference it is possible that the ARC system was not well matched to the room or the speakers and the Naim was, who knows, but the point is moot, people will like what they like and sometimes a different sound is what that person was craving.

"There is nothing either good or bad, but thinking makes it so" - Shakespeare