Here is a list of usefulness and mechanics for each follower.

Fiorayne

She does everything but nothing at the top. Not suggested.
Best with chargeblade; really good by being the first unlocked.

Galleus

By having wide range 5 in his armor set and using immunizers, power/might seed demon/hardshell powder it has execellent support.
Best with switchaxe that also holds a little bit of paralysis.

Luchika

Best in damage with both LBG and Bow.
With HBG she can help with KO (sticky shot); with bow she uses the affinity arc-shot and has paralysis coating that can help.
Drops bombs on sleeping monsters.

Arlow

Worst in everything... please don't...

Jae

Best in damage for melee weapon; can help with paralysis if he brings the switchaxe.
​Can help with KO if he brings the charge blade.

Rondine

Consistently drop traps on weakened monster. Best in capture quest.
Can help with paralysis when she has the switchaxe.

Fugen

Really bad with weapons (tho hammer helps with KO). However he drops 1-2 status frogs x hunt, meaning it can actually add significant status control to the hunt itself.

Hinoa

Basically no damage dealt. However she has the best support in the game by using dust of lifes and escurgots.
The hunting horn has:
  • Health Regen
  • Attack and Defense Up
  • Heal Recovery (S)

Minoto

Basically no damage dealt. However she can attrack the monster attention with its stinkmink.
The hunting horn has:
  • Stamina Regen UP
  • Divine Blessing
  • Sonic Barrier

Utsushi

Ignore all weapon but hunting horn... he has only 1 utility and is buffing you.
The hunting horn has:
  • Blight Negated
  • Attack UP
  • Elemental attack UP