Getting a taxi from a hotel is extremely easy pretty much anytime, let alone at 6a.

One of the reasons I suggested you switch your HND flight to one that departs from SHA is that the taxi ride is ~15 minutes v ~45 minutes (and y50 v y200). But, of much greater significance, is the relative speed/efficiency of the entire departure drill. Basically, you can comfortably show up at SHA at t-70 whereas I rarely risk going below t-120 when leaving from PVG.

Of course, if you can manage to through check your luggage, the calculus might change a bit, especially if your bags are unwieldy. Personally, I'd suck up the toting inconvenience (i.e wheel cart along in the smelly taxi queue for 5 minutes) if it yielded me an extra hour of sleep and a more enjoyable overall experience.