I found this[1], which summarizes nicely. Basically, they are almost equally as bad for your liver, and that was with one of them taking 21 shots of vodka[2] once a week, which left him insensible, and actually in a dangerous medical state.

1: http://www.bbc.com/news/health-32798569

2: I assume measured to 25ml which is the low end of single shot size, to be in line with the standard units of alcohol they mentioned.