The question is, a continuous footer or piers, which am I better off with?
Unfortunately, there's no simple answer to your question.
By footing, I assume you mean a thickened slab edge that extends 30" below finish grade. If we assume a minimal 6" of exposure, you will be forming a 36" deep slab edge. Since concrete exerts 150 psf of pressure for every foot of depth, your forms will need to resist 450 psf at the bottom i.e. they will need to be pretty stout.
In addition, the haunch itself will eat up a lot of concrete. If we assume a 45 degree slope and a 12" wide haunch, it will take something like 1/4 cy of concrete per running foot over and above the 5" slab itself .
On the other hand, someone - probably an engineer - is going to have to determine how many piers you need and what type of grade beam will be needed to span between them. The piers themselves will require several additional operations to excavate, form, reinforce, place and backfill. You'll still need a thickened slab edge to act as the aforementioned grade beam.
At the end of the day, it really depends on how your contractor prices the work. I would opt for the footer (thickened edge) and my guess is that it would be less expensive. I don't like the idea of 'frost protected' piers connected to a slab that isn't.
If you want to spring for some rigid insulation under everything to keep the frost out entirely, then it's a moot point. Since we are on the subject, maybe ask the inspector if the code permits a 'frost protected shallow foundation'. That might be the best option of all if it's approved.
