Hi Zeev,

The main difference is that Carmelit is an (underground) train pulled by a cable which is the definition of a funicular :) Subways are never pulled by cables. English wikipedia also calls it a funicular: https://en.wikipedia.org/wiki/Carmelit
Also see the Hebrew article on funiculars which in particular mentions Carmelit: https://he.wikipedia.org/wiki/%D7%A4%D7%95%D7%A0%D7%99%D7%A7%D7%95%D7%9C%D7%A8

Which aspect of a subway do you currently not represented by the data of Carmelit in OSM?