I don't have a kamael but ure cuestion is wrong, coz' the element it's variable depending of ure enemy, and for stance i think the better is wind, coz u can stop nuke casting from enemy...in any case u need to know how to turn ure instances depending the enemy, water= slow movement, earth=stun, fire=fear if i'm not wrong
Question is fine. Wind is best < 90, where you should be only focused on PvE, IMO. Water is decent 90+ for PvE.
PvP-wise they're all on par because geared characters will have 200+ resist to everything, anyways.
Proc on Wind > Water > Fire > Earth.
Earth is virtually useless for PvE pre-95 (and probably after) and Fire is pretty neutral but Kartia 90-94 resists fire, which is something to consider.
To start off, I'd go Wind. Lots of MOBs in Altar/Swampland are Earth Attribute. All of SoA Nursery and pretty much all of the inside of SoA (at least Croak and Reptili are). Harnak on the hither floors are full of Earth Attack MOBs as well.
Below 90 Wind > Fire > Water > Earth
90+ Wind > Water > Fire > Earth
95+ I don't know. I'm not there yet.
For PvP they're all on par and the only thing you have to consider is the proc, which Wind has the best one (better than Water > Fire > Earth, IMO). Everyone will have a ton of resist in PvP and you really shouldn't be concerned with PvP until at least 93 or so on a Nuker. Dmg penalties from level disparity affect this class more than any other.
Elemental Crash is the only targeted nuke that has a chance to cause knockback in Wind Stance, so just avoid using it if you're single-targeting in a group and want to avoid knockback.