Bösendorfer vs Yamaha
Comparing a Bösendorfer with a Yamaha grand is really a comparison within one family, because Yamaha has owned Bösendorfer since 2008. We sell reconditioned Yamaha, so allow for our leaning.
The short version
A Bösendorfer is a hand-built Viennese luxury piano with a warm, singing tone and a very high price. A Yamaha is superbly consistent, beautifully made, brighter and more precise, and costs far less. Yamaha runs Bösendorfer as a separate marque precisely because the two are different things.
Tone
Bösendorfer is mellow, warm and transparent. Yamaha is clear, even and bright, and carries and records well. Which you prefer is taste, not quality.
Price
This is the gap. A reconditioned Yamaha grand from Japan costs a small fraction of a Bösendorfer. For a fine grand in a normal home, it is superb value.