tamte

it's most probably caching of the acceleration structure
it seems that Ray SOP is able to detect that the collision geo is the same among all the iterations and therefore computes acceleration structure just once, while VEX intersect function is probably computing a new one each iteration
just a guess though

Vellum Solver SOP is superior in almost every way, it can be used in a spring SOP like quick&dirty way if you want, what exactly are you missing?

it's ophidden cause there is vellum now
you can opadd it or opunhide if you want