The flexibility of being able to choose a value for X is great because we might have an early-game case of wanting (or needing) to cast it for X of one or two, or we can wait until late-game and sweep a much bigger battlefield
Its universal compatibility means you'll never outgrow it
This is because those counters are put on as a cost, not as an effect
KRAZY KOW IS KRAZY, look at those huge eyes bugging out and the completely crazy expression she has and those mighty arm muscles and the fact that she's beating the farmer so hard that the milk's spilling all over the rest of the cards
Aang, Swift Savior / Aang and La, Ocean's Fury Aang, Swift Savior / Aang and La, Ocean's Fury is interaction in the command zone and a massive creature once transformed
Hopefully you will destroy your opponent without her ever getting back into the game