i have moved from mx518 to xai and i can easily say xai is an awesome mouse ! i dont know much about internal parts but it is very comfortable and it glides like no other
ive also used ikari laser for couple of days but it wasnt for me (its a palm grip) the thing is i tend to pick up the mouse when i do full turns and with ikari its really hard to pick it up ..
another plus for xai is it can be used by both types(claw/palm grip)
(ive been using xai with SS 4D mousepad and had no problems)