Science, Science, Science, don't know to be honest - at least they are half in their habitat (salt water) not as fat so PROBABLY better.
They also look cooler as they last a bit longer, I started off with these for a month,
However, Lionel took time taking to frozen, but when they take the first the second will soon follow, my dwarf did not eat for a month as I did not have small enough fish for him - he had no choice.
From reading your post, get the shark on frozen, lion does not like, so will leave alone - do not worry about lion fish - worry about everything else, lol
/try everything you can get your hands on, mussles, prawns, lance fish.
Do not put the fish into the water, drag them across the waters surface, not showing the stick (scared the living daylights out of my dwarf)
I used to also tease with my fingers just poking through the water - be very quick, lol.
It only takes a taste - the rest is history - literally