Attack won't be noticeable (and in many cases useless) vs. many targets because Y/G/K all have large attack bonuses so you are probably already at cap vs. a lot of targets. The only thing your meat is giving you in merit pts etc. when it comes to YGK is str.
Kaiten has no attack bonus, so it performs worse and worse compared to Gekko the higher level/defense of a mob. Kaiten is noticeably better in high buff situations and you can see Kaiten tear it up here with enough attack behind it. It always struggled vs. HNMs without huge buffs behind it. It just so happens that people never exp on era merit level mobs here & dyna mob levels are way higher.
I think a lot of people have incorrect recollections about retail (especially about damage), like people seem to think Amano Y/G/K were stronger than Hagun

Amano strength is in Kaiten, damage proc, acc, & better white damage. SAM WS damage is fine, SAM is more than fine.