I am a former Navy F/A-18 pilot and am now in med school. I am also a CFI and have my ATP. I have plenty of friends who are now airline or cargo (FedEx and UPS) pilots. I will say this about being an airline pilot: it beats a desk job. In fact it isn't a bad job at all. However, it is a pretty crappy career. At the higher end it is all unionized. You don't promote based on skill, you promote based on time and people above you retiring. If you get in with the right company things are okay, but the wrong one and things blow. Even guys in the right company worry because Pan Am was the best ... Until they disappeared. Same for Braniff and United had the best contract in history that was signed in 1998 or 1999. Everyone wanted United and guys who couldn't get in and went to Southwest were laughed at. Guess who's laughing now? Not the United guys.
There is a massive wave of mandatory retirements approaching and it will continue for several years and not nearly enough qualified applicants to fill the void. You will have to work some seriously crappy jobs to build your hours as even regionals require copilots to have an ATP, which itself requires 1500 hours. You also have to go where the job is because there aren't always open jobs where you want to live. Having said all that, it still beats a desk job and is way easier than med school and residency.
Some of my friends are happy with airline life, but the ones who were most like me are not happy with that life. For me, during my first solo multi-leg cross country flight in a Hornet I was bored out of my mind with about 2 hours at 36,000 ft and nothing to do before my next turn or decent. That is airline flying: take off, auto pilot, land. Repeat as necessary. If you are okay with that, you can see some cool places if you are on a good route and schedule. I was not okay with that after the stuff I was used to flying Hornets.
Flying is awesome and I will continue to fly on my own. The forked tail doctor killer thing comes from the fact that many doctors had enough money to skip simpler airplanes and buy right into a fancier one that was higher performance. Add to it that doctors tend to be a bit arrogant, though definitely not all, and they didn't train as much as they should have - it isn't like driving a car or riding a bike. That was the cause for that reputation. The new doctor killers are the high performance singles like the Cirrus SR-22 and the Cessna Corvalis.
DocB is right that you will generally be less competitive than the military guys, but with the impending pilot shortage that won't much of an issue. He is also right that you can pursue the double major and see what happens. Let's face it, if you can't get good grades or get a decent score on the MCAT, the doctor route is off, but no one cares about your traditional classroom scores in aviation. Then again I had a guy come to meas a student last year. He wanted to be a doc or a pilot and decided that he would try pilot first since it was cheaper and easier to get into. He puked for three straight flights and quit.
Overall there is a lot of similarity in that both require physical and mental aptitude and take years of training. Both also are relatively independent forms of work where you make most or all of the decisions, but are responsible for those decisions at all times. You can PM me if you have specific questions.
