There are arguments on each side. (And as a lawyer, this is how I look at everything). :)
Pros for Tuxes: More formal, more uniform, easier (everything is already picked out and included).
Cons for Tuxes: Expensive! Paying as you would for a suit on a tux you'll only wear one day. And apparantly the shoes are an issue. (See my dad's blog: http://poorweddingdad.blogspot.com/) Hehe.
Pros for Suits: Less expensive, can keep forever, often really can't tell the difference between a black suit.
Cons for Suits: Adds headache to try to find the right suits, at the right price, in all the right sizes; have to find matching ties (or coordinating ties); not uniform.
What's your vote? Suits or tuxes?
And can anyone even tell the difference?