When you open the bottle of "hardener" and it makes smoke from the humidity, then that's real epoxy. I used some under a fume hood at one job. I made prototypes for racing bicycles in pressurized molds.

Looking at name brand vinylesters and name brand consumer boat epoxies, the vinylester(epoxies) have equal or better elongation and tensile strength. It depends on what you buy, but I wonder if consumer versus OEM epoxies are different enough that VE and consumer epoxies are about equal? Some VEs are good for higher temp (engine room), too.

Don't forget to compare exotherm values.

That isn't something I think about lots, honestly.

I am interested to hear what you think about it. I can see tuning the process, and worrying about shrinkage- both of which seem like you can control (or lose control of) more with VE/PE over epoxy.