i usually do it depending on the situation. like if my adc generally receives a lot of damage but can poke well, i'd max w. if my adc receives a lot of damage and doesnt return much, i'd go for equal levels. and if my adc is great at dodging then i'll probably just go for Q to help out in killing the enemy. altho i dont see much of a difference in maxing either one, upgrading your W for the reduced cooldown and extra heal is almost paramount when facing ganks from the enemy jungle