The difference is there is no need for a ground occupation. It would be a solely naval (and possibly Air Force) campaign - so the number of potential casualties

The difference is there is no need for a ground occupation. It would be a solely naval (and possibly Air Force) campaign - so the number of potential casualties and time scales is much lower. China's naval power is massively far behind the US, as long as surface vessels stay out of range of Chinese surface to surface missiles they are safe. US submarines are pretty free to act, and scare the hell out of Chinese sailors, in the Taiwan straight. I doubt there is an American naval battleplan more developed than China attempting to cross the Taiwan straight. China's hopes rest more on missile attacks on Taiwan forcing surrender than an invasion. Subduing populaces by ariel attacks is surprisingly hard and counter productive, and nothing is more likely to turn pro-China Taiwanese away from their views quicker than that.