Apple stock has 10x'd under Cook since 2011.
Microsoft was flat under Ballmer.
So ummm, maybe a slight difference in performance.
So ummm, maybe a slight difference in performance.
The one that hurt Microsoft was the EU decrees. https://en.wikipedia.org/wiki/Microsoft_Corp._v._Commission may remind you of that.
That said, the one thing Ballmer did right is that he took on the difficult problem of locking down Microsoft products on a security front. This was a hard and thankless task, but absolutely necessary in the long run.
Ballmer became CEO in 2000. But Bill Gates continued being involved in day to day operations until 2009.
Considering that Microsoft got religious about security in the 2000s, and this was a shift in corporate policy, I give credit to Ballmer.
But ideas are a dime a dozen. I give credit not to coming up with the idea, but to actually putting in the elbow grease. And there is no question that Ballmer put a lot of elbow grease into keeping the initiative going.
A company is more than its stock price.
In fact according to the CAPM economic model, it is impossible. The assets of the company decrease by the money spent on buybacks, which matches the value of stock bought and destroyed. This should leave the price per remaining stock unchanged.
All are second order effects.