What do you mean - "young AGAIN"??
I'm young - STILL!!!.
To answer your question without the smartassery - if I had to do it all over again, I'd stay in the Infantry.
I did an undistinguished stint as a 031 a LONG time ago - then I got out. I re-enrolled as an Adm Clk (831), which trade was amalgamated (along with Fin Clks and CEP Techs) into RMS (836).
Although I had a good career as a support guy - and I'm proud of it - I really think I would have been happier being supported - rather than supporting. It's a mind-set thing, I think - friends of mine (with as much or more TI than I) are extremely happy in their support roles - and wouldn't think of becoming a Cbt Arms guy.
It is, of course, a hypothetical question which has no real meaning in the greater scheme of things. I re-enrolled as an Adm Clk because it was the first trade they offered, I was unemployed (during the LAST great economic downturn in '82), and I had a wife and child to support. If that same set of circumstances were to re-occur - I'd make the same decision.
Roy