This last application cycle I applied to 2 different specialities and noone was any the wiser. In the end it all worked out fine. I had 2 different sets of advisors, wrote two different personal statements, and had 2 different sets of letters of rec(3 for each). On my matchlist I alternated specialities. I went to 2 different sets of interviews. I applied to about 70 programs, went to about 40 interviews, and ranked 22 programs. I matched at my top choice. Its none of the program's business, if you applied to different specialities. Your allegencies should be towards yourself and getting into the residency of your choice. Who cares what the programs think? 6 years after this application cycle programs will not remember you, heck after this last application cycle programs will not remember you. You need to keep your mouth shut though and not volunteer extra information whether its in your personal statement, or during your interviews. It noone's business, especially not the programs you applied to.
One kid in my class, essentially did what every one here is suggesting the original poster to do. He applied to 2 different specialities and then proceeded to disclose this fact to everyone who would listen. He told his 2 sets of advisors (they weren't happy), and mentioned it during his interviews with his interviewers (I'm sure they were not happy). The thing is he would mention the fact that he was applying to 2 different specialities unsolicited to people. Noone asked him beforehand if he had done so. He did not match during this past application season and has to try again. If none asks, don't tell. The application cycle is only about 5-7 months in length and determines at least for the next year, and at most for your whole career, what you will be doing as a job. Keep your mouth shut during that time period. In the real world people apply to different career fields all the time. This process is no different.
Some people just need more time to make their decision as to what job/career they want. Apply to 2 different specialties is a way to make a final desicion (albeit not the best way to do it). The cons of applying to 2 different specialities is not getting "caught" by the programs; Its the logistics of getting 2 sets of letters of rec, meeting with 2 different advisors, applying and traveling to lots of programs, and doing this is very very expensive. Applying to 2 different specialities is very expensive. Because of that I would suggest pick 1 specialty to start out with and to go for.
In the end I'm happy with my decision, albiet a lot poorer. I had to do this to make up my mind, which I did. Advice: don't apply to the 2 different specialities at the same institution, its just not smart. They probably will not find out as the appliction season time frame is so short, but why risk it. Also most of the time, one department/residency is stronger at a certain institution and picking which to apply to an easier decision. (This is of course excluding very elite institutions were there is a likelihood both specialities you are applying to are strong).
Good luck, and get started.
