I'm on the side of Luigi, it all started when my cousin and I were about 7 and playing Mario Kart 64, he'd always be player one and would always pick Mario, so I went for Luigi, mostly because my name begins with an L :)
Also, heres the reasons why I think Luigi is better:
1 - He breakdances in Mario and Sonic at the olympic winter games.
2 - Backing the underdog means its way more satisfying when they win.
3 - In Luigi's Mansion, Mario was beat and turned into a portrait by the boos, and who defeated them all to save him? Luigi.
4 - Luigi's girlfriend doesn't get kidnapped all the time, I bet Daisy kicks the asses of anyone who tries to kidnap her =D
5 - Mr. L - Coolest alter ego ever.
Why are we even discussing this?
I was bored and wondering what people would say, reading the responses has been fun =D