You'll have a lot more protection from pregnancy if you use it. Never just use condoms or birth control alone - do the smart thing and double up. Then you can kiss those swimmers goodbye. The cons are side effects. They're rare, but they do exist and it's important to tell your doctors about other medicines you're taking that could possibly interfere with the birth control. I have three sisters and a girlfriend. That's how I know.
Pros, can fix acne, substantially reduced "risk" of pregnancy, regular period cycle
Cons, Class A carcinogen and more deadly than ciggarettes (All forms of birth control pill fall under this), Contributes to risk factors for several different cancers multiple other things that I just really don't want to list right now. Instead of taking my word for it, just read this. This is just one of many sources that can be drawn from in this regard.