First, when you referred to the "VT 150" I suspect you meant to refer to the VTL ST-150. Let us know if that is not a correct assumption.
Second, and consistent with Mapman's comment about system synergy, in the case of the power amp it seems to me that which is likely to be "better" is the one that is a better match for the particular speakers it will be used with, which have not been indicated.
The VTL ST-150 has a single output tap, nominally rated for a 5 ohm load, and **claimed** to be suitable for use with 2 to 8 ohm loads. I believe it also provides only unbalanced inputs.
Your ARC REF 110 has 4, 8, and 16 ohm output taps. Like many ARC power amps, in comparison to most competitive high quality tube amps it has a relatively high damping factor (spec'd at about 12) and a correspondingly lower output impedance, presumably accomplished in part by the use of greater than average amounts of feedback (again, in comparison to most competitive high quality tube amps). That will tend to increase its suitability for use with speakers having substantial impedance variations as a function of frequency and that were also designed with solid state amplification particularly in mind. However that increased versatility might, at least to a very slight degree, come at the expense of the adverse sonic effects many believe can result from the use of significant amounts of feedback.
VAC amps generally use minimal or no feedback (adjustable in some cases), have lower damping factors and higher output impedances compared to ARC amps (for a given output tap), and have multiple output taps including taps suitable for driving very low impedances.
As a very happy VAC owner, I will add that its president and designer Kevin Hayes is in my opinion and the opinion of many others second to none in responsiveness and customer support.
Good luck in your search. Regards,
-- Al
