Gave up on power trowels for small jobs, and it's a mixed bag.
I stopped using power trowels on pours under 500 square feet to keep things quiet. The hand finish looks better to me, but my partner says we're wasting time. Who's right here?
The second pass with a 220-grit sandpaper. In my experience, that step is what gives you the glass-like finish. I skipped it once on a table top, and the difference was night and day. It adds maybe an hour to the job, but you can feel the quality. Your mileage may vary, but I've never regretted taking the extra time. It just makes the whole project look pro.