If you practice jiu Jitsu, your clinch game would be deadly. Age is not a question when it comes to clinching or even kicking. Land a nice low leg kick on someone, make them think twice of even going near you. Boxing is a way less superior art, as a fellow martial artist you should know that.
If you wanted to box simply for the love of the sport, that would be different but you're asking to dominate stand up while not taking it to the ground, Muay Thai is the most superior and it's not even up for debate. Using Legs, Knees, elbows, hands are better than using just hands.
As for age, putting someone in a clinch where 99.9 percent of people don't know how to get out of (even Rich Franklin) and feeding them knees is way less taxing on the body than standing there and throwing hands using reflexes. With age, reflexes and speed decreases as well, so with your logic, Muay Thai is still the route to go.