Fin Briar enhanced: 2.3x with 50% def ignore = 4.6x.
Snowpetal enhanced: 2x with 65% def ignore = 5.7x
Gilgamesh can pretty easily reach the 300% atk+ cap, while Firion struggles there... but Firion has tons of killers all over the place, and I'd have to math those out to figure out who is truly better.
On first glance though, it does look like Greg is probably still the better capper with enhanced Snowpetal and Weapon Collector. But with the robot trial rewards Firion definitely can hold his own.