What a better pre-amp Arc Ls-27 or Ref-3

I went from the LS27 to the Ref3, and found the Ref3 had a cleaner, clearer sound, less tube like. Both were excellent but the Ref3 was a step up, and the Tung-sol 6550 NOS tube made it even better.

Before I try to answer the questions above, I would like to say how much I enjoyed my time with both units.
If you require big bass slam, the LS27 or REF3 may not be what your looking for. That being said, I don't recall feeling I was missing anything in the lower frequencies and the REF3 certainly had good bass extension, just not big bass. The 3 had a bit better resolution, detail and neutrality. The 27 had more of the old school Audio Research warmth and what some refer to as tube magic.
Trying to compare the REF3 with the Ayre KX-R would be difficult. The KX-R is nearly impossible to place, like one component has been casted out from the chain, it's beguiling presents emulates being moved from row 20 to row 7.