At least in the US, insurance rates are mostly driven by hull value and secondly by pilot experience. I checked last year and a Bonanza was slightly more than a Cirrus having the same hull value.
The big negatives for the BRS system are cost (initial and 10 year repack), weight and space. On a twin that might mean a huge penalty.
There are a lot of scenarios where neither a second engine nor a BRS system help i.e. pattern stall, botched landing etc. where neither help.
Among Cirrus pilots there was a telling fatal in Florida where the pilot was known to be dismissive of BRS. He had an engine failure and decided to do an off field landing on what looked like good ground. Small wheels, 3400 max gross and a 59 knot stall speed led to a poor outcome. He and his wife died. There was another in the Florida Keys that had a better outcome without using BRS so it is just an odds thing. Stll, a Cirrus is very different from a Cub.