I consider a p88 compact a step down from the standard p88. they made a lot more comopacts and sold them at a discounted price the last few years they were on the market. the p88 standard is a much rarer and more special piece, so expect to pay a premium for it.
I have both and love them equally. I find that the grip of the P88C fits me better, not as big as the fullsize. Otoh, I don't really like the P88C safety/decocker mounted on the slide. I would prefer something like the P88 fullsize lever or the P99 decocker. For me the fullsize seems more accurate, ymmv.