Both are neccessary.

Anima is for casuals who won't run out of it nearly as fast.. and won't have as much gil either.
Airships are for hardcore who will be low on anima but have lots of gil - From the tone of Yoshida's comments I'm guessing airship tickets to cost 20k or more.

I think its a great system that helps reinforce FFXIV's 'all-of-the-above' approach to playstyles.