I'm flying China Eastern to Vietnam, and I have the following long stopovers.

Going out:
Land 5:10 AM in PVG, depart PVG-SGN at 22:15 PM. So this is a 17-hour stopover.

Coming back:
Land 7:05 AM in PVG, depart PVG-YVR at 0:05 AM, so another 17-hour stopover.

I had been thinking of going into Shanghai, and possibly crashing at a hostel for a few hours, while attempting to do a bit of sightseeing.

But now I am thinking if I would be better served to use each of these for a day's work (saving two vacation days) and resting, using either a lounge (I have no status, so I'd have to buy a lounge admission) or maybe an airport hotel.

Given the timings, what makes sense here? I've never been to China before.

If I forget about working, what would be a good way to spend each of these days?