I'd say pick the Aramis. Good general, all purpose, great density, great longevity fragrance. Polo Green after that, but I think Aramis is the more fun of all four.
Chanel Pour Monsieur, NOT the concentree version, is a great fragrance for sure, but it is hard to find and it doesn't last very long on the skin. Many members will post here saying it is a perfect example of its category and a milestone in mens fragrances, but beautiful and refined as it is, it isn't as much fun as a good old dirty mess about fragrance like Aramis. Get Aramis. You'll be able to wear it and feel appropriate with it 25 times for every single time you'd feel like you were doing justice to Chanel Pour Monsieur. You don't need an occasion for Aramis, but you do for Chanel PM. That's my point.