i also find the 5D2 sharper than the 5D even at f22 (the 90 TS seems to hold up a bit better at f22 than the 100M), and live view is a huge advantage for subjects that don't move
if i were shooting jewelry, i'd certainly try Helicon Focus both for overall sharpness and the ability to use smaller apertures to control the area of sharp focus relative to background (again, live view really becomes useful here as well), but in general if the 5D2 is softer than the 5D, then there is a problem somewhere