Stated in modern terms, the '71 is a 62cm bike with an enormous 61cm TT, and the '74 has a crazy short 56cm TT. The shorter '74 TT would be easier to sit upright upon.

Wheelbase wise, the International is supposed to have big tire clearance, and went from 46cm chainstays to 43cm. Either should be capable of decent tire size and fenders, but the '71s long stays might make the handling pokey and add unnecessary weight.

It sounds like the International got a little sportier, lighter and easier to fit between '71 and '74. Which seems like the way road bikes (other than touring) continued to trend into the '80s. You can argue the merits of the change, but that 24" top tube wasn't doing most people any favors.