I've never had a post-Vulfix Simpson, but from what I've seen, the hair on the Super brushes seems to be different. 2-band knots seem to have disappeared. The handle material looks slightly different in color but that may be due to differences in lighting and photography. The lamp-black stamping is gone, replaced by engraved model names. The main difference that I see is that models such as the Persian Jars and the Tulips are now made with different, much less curvaceous handle shapes. By all accounts, they are very good brushes, just different from the original ones.
I agree, probably better made than the late model Pre-Vulfix specimens. They just don't have that mystique that the pre-vulfix brushes had. More of a hand made individual product than a mass made brush.
Lees Razors is always a good choice especially if you need service after the sale. I can't see any difference in the material used in the handle between my Vulfix era Chubby and 2 original models. There is a difference in the grading of the hair, the lofts in some models is a bit longer but the Vulfix era models are very good brushes on their own merits. I have a Chubby 2 in super that is a great brush. Call Lee at Lees Razors, tell him what you want in a brush and he will come up with a model that will suit your needs. These are quite good brushes, just not quite like the old ones.