Me, Beta, and Isandwich were talking on irc about how no one uses panthers becasue they cant catch lynx and cant fight tigers.
You already have the answer guys. Just a matter of using your brains a bit here..
If you can't catch Lynx with a Panther, you don't use Panthers to chase down an army of Lynx. Obviously, you use Lynx to do the job.
Panthers might not be able to stand up to Tigers, but they can easily stand up to Lynx.. Right ?
So, if you got superior units, but can't catch or give chase to your enemy, what do you do.. ? You either block his movement, or make him come to you.
-By this I of course mean you use natural bottlenecks on the map. Place some Panthers there, and a moving Lynx army will have a thougher job going through, than if you were guarding it with Lynx. So as long as Lynx units are in the offensive field, Panthers have their value. However, when Tigers are introduced as the main offensive unit, Panthers will be obsolete.
Me, I always prefer high speed and manouverability over armor, since I will then most often be the one who controls where the battles takes place. However, when you get Tigers, their superior firepower will do the same trick, because with a army Tiger moving somewhere to strike, your opponent can't avoid the coming battle. In both cases I take control over the battlefield.
Using Panthers to force my opponents early Lynx army to move in a certain direction or avoid a certain area still allows me to control the battlefield. It's just that I've used the above so long, that is what I feel most comfortable with.