Fish oil pills vs. Cod liver oil pills?

I want to start looking into taking fish oil pills or cod liver oil pills. Friends have to told me the benefits of both, but I want to weigh the pros and cons? I hear that cod liver oil pills are good for hair and skin and that fish oil pills are good for mood, and heart, memory, etc.., I don't though, want to take both everyday. I need to get my skin and hair in good shape and I feel that the cod liver may do the trick, from what I been told, but the fish oil pills you have to be careful because of mercury levels? Are the Omega 3 fish pills ok and do they contain mercury or is that just for cheaper brands? I also want to find pills that have a lemon taste or something so I don't burp fish, ewww!