Modern Carbon Advantage VS Vintage Steel

Hi,

I'd like to have the forums input on a simple question.

I train very frequently on a 2 x 12 KM stretch (back and forth, no cars, super flat, asphalt, non-stop).

I do this on a classic pro CX bike loaded on a RX100 1x8 setup with brifters and Spooky cantis.

Frame is ex-pro (no eyelets,...