A standard 13b rotary is as heavy as a ca18de or L18 all without ancillaries.
Rotaries are compact hence their popularity in conversions.
With all ancillaries the twin turbo 13b is only 30 or so kg lighter than a fully dressed Gen 3 v8. An alloy alloy race 13b is just sub 100kg fully dressed. (racing beat - read expensive)
Yet still cheaper per hp than same weight race engines producing same NA hp.
Rotaries are thirsty, noisy and hard to find realible second hand ones as they
are usually abused beyond redline and rebuilt with re-used seals as a dodgy cost cutting measures by many backyard and by so labeled professional builders who know they will last 5km or a little more guaranteeing money in their pockets.

Id say the ca18 over the 13b
However id prefer an L series with Ka12e head or good L 8v head and turbo
over the complexity of a hydraulic 16v head.
L series engines are legendary for more than one reason and remove the need
for pollution gear.