The older dog sounds better to me , I'm basing that off the temperament not energy level. You can put the male on a diet, get him healthy, so the weight doesn't play a role with the hips if they become a problem.
Misty- Samoyed Mix
Tannor- Golden Retriever CGC
Robyn- German Shepherd CGC, TC
Midnite-German Shepherd CGC, TC
Brennan- Golden Retriever CGC