Since 1995 the Mark V (and ALL variations of that action) have been built here in the U.S. The Vanguards are still built in Japan.

There is not difference (quality wise) between the two IMHO. The Japanese guns (both VGs and MKVs) are recognized universally for their quality and fit and finish. If anything the American MKV versions have less impressive wood in the regular MKV Deluxe versions but I don't think that is as indicative as a quality issue as it is a basic supply and cost issue. Gorgeous wood blanks are harder to get and have REALLY gone up in cost in the last decade!
RA