Back then I had a lot more self respect, while I lacked confidence. Now, I have embraced self-hatred, and have a lot of confidence, probably misplaced.
I think my older self would win. My younger self would be amazed at my success, yet I am envious of the potential I had, and wasted.

My older self would win. Back then I was completely annoying and knew so little about the world. I was also more self-centered.

Actually you have already seen that here.

I like to think it would be a contest to see who could lose.
My 18 yo self not wanting to see a weak old man in his future, and the old man not wanting to set the kid back.

I would probably lie to the kid. Making him think there was fame and glory in his future, and that he would come to be me after.