Err no question about it, I have both sitting here in front of me, I much prefer the AR 610's.
I have lived with the Seigfried's for a year and tried many different tubes in them, the best sounding were the EAT KT88's but there reliability was not so good (a biasing issue I think) I ended up with matched GE 6550C's. Which were far better than the stock tubes.
We also always had a channel imbalance issue which with the 610's has disappeared.
We have just received a pair of REF610T's and the build quality is superior, the sound is much better IMHO, the soundstage is wider and deeper with superior transient speed. The bass is deeper and the resolution is stunning. One aspect I like very much is vocals have a 3D perspective to them, you can clearly hear everything that is being sung. My wife and I almost stopped listening to music with the VTL's now for 1st time in months we have had several late night sessions, which says it all really.
System they are being used in is Wilson X2's/Aesthetic Callisto & IO with dual power supplies/source is Rockport Sirus 3/CEC TLX, Audionote DAC 5 and cabling is all Transparent.
Oh and Dave uses a number of different amps, John is using the 610's at home with Maxx 2's. Wilson's policy is to not specificaly recommend components.
If you send me an email I will send you some photos.