Who is the king of Tube amplification between these two brands?
I had a AR set up for a bit... went to Mcintosh, then over to VTL, will NEVER look back. Clarity, open, spacious, clean. Running Siegfrieds, 7.5mk3, and 6.5mk2 phono.... lights out
I've had experience with both companies.  Had a 6B preamp / 90B amp setup for years.  Switched to VTL 85.  Sold the 6B.  Bought new modified 6A, bought new 85, bought older ST-150.  Love both.  Think ARC excels at preamps, expecially phono stages for MM's in their older gear.  Think VTL tube amps sound more "classic" (for good or bad) but ARC's have very nice sounding clarity in midrange.  ARC service is good, but restrictive (no mods allowed) and pricey.  VTL service is non-existant.  Can't even get an email response on their own email website link.
VTL is out. Horrible service unless you just spent 30 grand on their gear they won't give you the time of day.  It's ARC or VAC.