I'd lean toward the FBI. Simple fact is you can work the fed side until your 50 yrs old, retire and you'd still have 15 years to work as an airline pilot. You'd be getting a good pension.

FBI retirement
https://www.fbijobs.gov/333.asp

But just like flying being an LEO is a special calling and I don't think you should do it if you truly don't believe your willing to sacrifice for the job. But you may like one and not the other. I'd give both a shot, who says you can't?