Neither is competitive. Granted, both have programs that are competitive, but both have programs that are not competitive at all. If you cast a wide net, you'll almost definitely get a spot.
That said, they are VERY different fields. I was choosing between the 2 in med school as well. Then I did a Sub-I in family medicine and realized I only really wanted to take care of the kids. To me, the outpatient management of HTN, cholesterol, etc. got very old very quickly. Peds allows you to do outpatient private practice if you want, but there are more paths that you can ultimately take than there are in FM. You can do anything from peds cardiology, to neonatology, to hospitalist pediatrics, to peds emergency, to allergy-immunology, to pediatric critical care and everything in between.
If you know you want to do outpatient medicine, then the question is this: would you rather manage chronic patients who are obese, smokers, alcoholics and have a million medications and health problems, or would you rather take care of babies who spit up and don't poop enough, adolescents, and a million kids with viral URIs and ear infections? I know outpatient medicine is a lot more than that, but if you look at the worst of each, that will help you realize which one you really can't handle forever.