To slab, or not to slab

I'm soliciting advice and design tips for a small observatory building
(thanks to all who offered their inputs in my earlier question about the
pier footing). Now comes the decision about the footing for the rest of
the building (10' x 12'). Is it better to pour a full concrete slab with
perimeter footers, or would it be better to use only perimeter footers
with a raised wood floor?

The climate here is dry, but day vs. night temperatures are sometimes
50F. Does a full concrete slab radiate heat all night and spoil the seeing?

Again, thanks in advance!