Distinguishing no 1 from no 2 is like distinguishing Ant from Dec

I had to explain the difference in toilet terms between number 1 and number 2 to Andrew today although he was arguing fiercely that no. 1 is something of more significance, the big kahuna, and it should be the other way around. He proceeded to state it was like distinguishing Ant from Dec, our fabulous UK TV presenters who are always paired up. That made me laugh the leap from piss and shit to Ant and Dec. Ant is always on the left so one system for who's who is that going anti-clockwise you get to Ant. His other system is that Dec is smaller and he thinks of decrement i.e. in "Mathematics The amount by which a variable is decreased; a negative increment" (thanks thefreedictionary.com). Can anyone help me with a system for no 1 and no 2?