I would do the 3500 for Audyssey XT32. It’s head and shoulders above Audyssey XT. I also agree with
@Pogre. Arc can be a PIA and quirky. Also, some TVs only pass lossy codecs and possibly only 5.1 etc., so performance can be compromised.
I don’t know all the details as ARC is something I think about as much as I think about eating Brussels sprouts.