As for comparision - they're both good tools. SD has some templates that are nice and very fast loading (even faster with a little bit of tweeking), and their tools are very simple and straight-forward. However, they havent kept up with the changes over at ebay and as a result you have to go to ebay and edit the listing after you launch it, if you want to use the new s/h info, new return policy bit, and last i knew there were a few probs with item specifics - but they might have been fixed (not sure).
SD's gallery and Auctiva's store window are both nice features.
In my opinion, Auctiva's checkout redirect is super nice to have! (even though some have had problems with it) And I really like how I can set up profiles for different parts of a listing and then a master profile based upon those sub-profiles, and then load all of that plus template into the lister! All I have to do is load it, add pic, modify description, set price, and launch. Very simple
I will stay at SD at least long enough to give the new inkfrog version a try in June, but I will also continue to use Auctiva.
Even if I stay at sd/inkfrog I will most likely also be here using auctiva.