Well I don't know if there is much of a difference, but I've ordered about 6 times from Tankzone's ebay store and have had my items arrive quickly and have had no problems so far.
I've found the prices on their ebay store have been the same and sometimes lower then other sellers with better reputations like pugwash and blueslatesman whom I've also ordered from.

Additionally I've had slightly negative experiences with some vendors who seem to have "can do no wrong" reputations.
I guess it's all up to your own personel experience. As far as I'm concerned they've worked out better than others.

Maybe they're more concerned with maintaining their ebay feedback reputation, which is another trend I've noticed with some vendors.

Rob>