I wouldn't say that BL is better than Osage, but that's mostly because Osage is more versatile and forgiving than BL.
BL has been my fastest bow wood, and it's made my favorite bows, but it's also failed on me quite a bit.
If I had one chance to make one bow, I'd pick Osage. If I had five chances to make as many bows as I could , I'd go BL.