You measure them by watching them play. Of course you can measure balance and coordination visually. Have you played basketball before? It's something you can size up almost immediately. Quickness, balance, coordination... and yes, Bird was superior in every way.
Bird was a much better athlete than people give him credit for.
Especially when he was young.
TP, you beat me to it. Bird might not have been fast, but he had lightning-quick hands and, believe it or not, pretty good to excellent lateral quickness. His wingspan, iirc, was either equal to his height, or slightly longer, but at least it wasn't noticeably shorter like KO's. It's a bigger problem for a guy who's supposed to play inside, anyway, imo, like Olynyk. Plus, I really hate stretch fours, lol, but that's just personal preference. I also hate when Kelly pump-fakes and then tries to drive the lane or whatever, because, honestly, he looks only slightly faster than Chris Mullin, who, again, at least had lightning-quick hands to be able to offset some of his defensive deficiencies. Dat billy goat has none of those things, and where are his post moves!? PLAY INSIDE! Ugh.