[old_tv_nut]

Difference in noise could easily be because the tracking of one machine just happens to better match the tracking of the source recorder.

In terms of sharpness, VHS basically has crap frequency response, which is coaxed into an acceptable picture by non-linear video peaking. This can differ from brand to brand depending on the preference of the designers, but you can see what's going on when you look at multi-generation VHS bootlegs, where more than one serial attempt to squeeze wine out of a lemon becomes obvious.

The short answer is to just use the one that's best.