It took several days to sort things out. I had some scales, tone exercises, a low piece, a higher mid range piece, and harmonics to compare, alternating each flute.
Eventually for me the Altus just didn't work as well for me, maybe it was the Z cut headjoint.
Both the Yamaha and the Sankyo played equally well. But I preferred the tone of the Yamaha, which had a solid silver body and sounded a bit warmer. The Sankyo sounded as good but was a bit "brighter" possibly because the body was silver plated.
As a bass instead of a soprano, I prefer the not quite as bright sound of the Yamaha.
Yamaha 677HCT; Emerson sterling silver flute, open hole, B foot, with an "8" on the body.