The Nashorn weighed 24 tons, one ton less than the Panzer 4H so I don't know why it's Panzer 4 engine and suspension would have been strained by the weight. Also it was reliable and if damaged easily recovered. The Jagdpanther had great protection and mobility but it suffered from the fact that it was on the Panther chassis and therefore had the same problems with complexity, difficult access to the transmission and the problem of recovering a 45 ton machine. I guess the trade off with the two vehicles is between protection and reliability/recoverability. Which do you value most? I read somewhere that while the Nashorn was succesful with a very good kill ratio it was never popular with it's crews, probably due to the lack of protection. Basically if you had to go into battle in a tank destroyer and were given the choice between them which would you choose? I guess most people would go for the Jagdpanther in spite of reliability issues as you would want all the protection, and therefore most chance of survival, that you could get. But I think the best German tank destroyer was probably the Jagdpanzer 4 as it had low height, good gun and sloped back armour. Unlike the Stug 3 it could take 85mm fire frontally. And it was reliable and recoverable.