I agree with what Marni, Owlie and OakLeaf have said -- your endurance and strength, even skills, come from riding more time, in whatever bike you have.

However, I will add one confounding, psychological, factor: fun. If you like your bike and it is fun to ride, you will ride more. If you decide to go the road bike route, I would suggest you don't go overboard. As you ride more and develop as a cyclist, you may outgrow your first bike.

Welcome to the fellowship of cyclists!