I sure hope you are planning on spending some time in both places before you move to either one. Being that you are in New York there is a lot to consider. Are you east coast or west coast. Believe it or not this has a whole lot to do with it. Are you a desert rat (Phoenix) or a tree freak? (Austin) Do you like trees? (Austin) Do you mind humidity? (Austin) Do you mind a good dust storm every once in a while? (Phoenix). Lots of brown landscape is what you get in Phoenix. Lots of green, green, green, is what you get in Phoenix. It's not a matter of sunny days and weather as much as it is what you like in your everyday life. Do you like mountains? Austin has "hills" not mountains.
Myself, I have lived in both places. I like the west coast vibe. I'm all desert! Don't get me wrong, Austin rocks! It's a great place to live. Phoenix is a bit crime heavy. There are some alternatives to Phoenix however. New Mexico is a fantastic place to consider as well.
Good luck my friend.
Remax / Lakeland