I am looking at becoming a Warrant Officer and currently building my packet. What are the benefits of Aviation vs Intel, and vice versa?

A decision you need to make based on what you want.

CW5 Jack Cardwell Chief has the best answer. I would say, since you are on the fence, go with what will have the long term benefit. I had flight dreams for a long time, and sometimes still do, but I'm entirely happy I never made the decision to go aviation, because it turned out that I am more passionate about what I do now.

I don't think you can be an Intel warrant without an Intel feeder mos or relatable civilian experience

I always wanted to be an aviator but that isn't what I wound up doing. Do whatever is necessary for you to change branch to MI. Realize ahead of time that all MI personnel will not necessarily be able to make the transition to Counterintelligence Tech (351L) or Human Intelligence WO (351M). I am including these links:

https://www.goarmy.com/careers-and-jobs/browse-career-and-job-categories/intelligence-and-combat-support/counterintelligence-agent.html

https://www.goarmy.com/careers-and-jobs/browse-career-and-job-categories/intelligence-and-combat-support/human-intelligence-collector.html

https://recruiting.army.mil/ISO/AWOR/351L/

http://www.army-portal.com/jobs/military-intelligence/351m.html

Don't be surprised if you need to return to the active component to become competitive. If you don't already have a bachelor's degree, plan on getting one.
To pass the background investigations you cannot have made any really stupid mistakes in your life (this included as a juvenile).
Good luck.

You must have a feeder MOS in order to go Intel WO. Aviation does not require that.

For any of the MI warrant specialties, you must already hold that enlisted MOS and have the ALC for that MOS completed. For Aviation, if you have the GT score, you are already eligible.

Aviation Career Incentive Pay, Flight Pay, and all around windows for your office vs. an office with no windows and someone else always taking credit for your work. Best of Luck!