At the very end, Hornacek's knees were shot. But I think it's very safe to say that he was still a much better defender than Jimmer.
http://www.basketball-reference.com/...3=&p4=&p5=&p6=
Hornie is a better defensive rebounder and has more steals per 36 minutes or 100 possessions compared to Jimmer. That's a couple of metrics.