TBI heads are 168cc (if I recall correctly) and they flow terribly... I mean pathetically. They flow about the same as a 1956 265ci head. Ridiculously terrible.
Vortecs are only slightly larger ports that are the best flowing production head GM ever made.
So, massively increased HP potential, no loss of torque, plus vastly improved chamber design that is far more efficient. Its not just about quantity of flow and velocity of flow, its about quality of flow. Of all the GM production heads, the vortecs beat them all.
Put it this way. Take a stock TBI engine and swap on vortec heads (with the obvious requisite changes) and the vortec will beat the TBI head in hp AND tq.
Comparing TBI heads to vortec heads is like comparing Taylor Swift to Taylor golf balls. No comparison.