Obviously, I chose poly. The only cons I have on poly have bright sides, and the only pro I see of monogamy definitely has a dark side.
Pros: freedom, validation of my natural desires and pursuits instead of condemnation and repression
Cons: societal judgment and having to 'hide'
De-cons (bright side): being in the minority and having a secret from the world can feel cool; I'm a bit of a rebel spirit, so doing taboo stuff (having multiple partners, threesomes, etc.) is really exciting and fulfilling
Cons: rigid relational structure/s (serial monogamy), no smooth transition from one partner to the next, relationships are like switches instead of sliders (and you are only supposed to have one switch on at a time).
Pro: the feeling of being the 'most' to someone
De-pro (dark side): enjoying the feeling of being the 'most' to someone has really questionable motives and roots. Being the most to myself is totally good enough
Me: Straight male, anarchistic polyamorist, hate labels
N: Straight male, best friend throughout childhood
M: Bisexual female, introduced her to poly
C: Bisexual female, 'girlfriend' of N before poly encouraged de-labeling
A: Straight female, newest in my life
I love them all.