hmmm... Well to be honest, a pro friend helped me with Kanako when he was still playing, andi only got her cuz she looks pretty XD (and had a bow) her quest is pretty easy if u compare it to others, but she unfortunately NOT burstable.

THE FOLLOWING IS MY PERSONAL OPINION:
Again, i got pro help with Victoria, because her quest is i think one of the hardest, pet-wise. She is a VERY good pet, as she builds con and str really well. she's also pretty good for bursting, but whether u put her into the team for dmg or assisntance im not sure :/

About the GS thing, I think it's good, but as fire technically has 3 atk-raising skills *i'm not sure* the factors that matter are probably the DURATION and the actual INCREASE. I think the gs increases the attack x3, so the other skills might just have weaker benefits, causing less damage, meaning less exp

Human pet bursting: http://wlodb.com/topics/2745
Koji's guide to pets ( u might've saw this before): http://wlodb.com/topics/15272

btw, about good pets, you can see every1's skills here: http://wlodb.com/topics/7926
and it sgood to get a pet of your element 'pair':

Fire + Earth (vice versa)
Wind + Water (vice versa)

BUT you dont have to follow this rule, as i think Victoria ( i was just lucky that i was Earth XD) is a good pet for most elements/builds. Eva is also good (i mean , mess is always good, right?)
and her quest is super easy ( i think irs only 1 fight in Inca) but the downside is that u have to get Charlotte first -.- + she tends to build wis and agi, which i guess isnt that bad XD

Well, I'm no pro, but i hope this helped :)

CREDIT TO THE PPL WHO CREATED THE ABOVE LINKED THREADS