I'm sorry Gaga, but Toxic is just epic!! I remember when I was young and the Toxic music video came out, I watched it everyday when I came home from school. That music video was soo cool then, it still is. Toxic is just better to me.
Both are great songs, but I'm going to go with Bad Romance. Better lyrics, vocals, and production. The video is epic too. Toxic is catchy, I actually like that song, but anyone could have done it. Now the video [Toxic] is pretty epic as well, one of Britney's classic ones. Toxic is more iconic since it has been around long enough stand against time. Hopefully Bad Romance will do the same