Ballmer would have driven MS into the ground if it weren’t sitting on more cash than anyone knows what to do with. He presided over an unprecedented period of aimless drifting and gradual decline. Completely missed the whole mobile thing.
Nadella, OTOH, seems to recognize that the glory days of having a monopoly (and the evil that allowed) are over. One company after another is getting out of the unprofitable PC business (Toshiba and Fujitsu are pegged to be two of the next, and Dell is desperately trying to re-invent itself).
I see encouraging signs of cooperation with others (e.g. the Linux community) instead of trying to stomp on everyone’s face, and with it, a new era of real innovation.