Here's my fav aeons and why:-

Fav looking Aeon
Name: Ifrit
Why?: The fire that rages from him and the way he uses it to annihilate his enemies, he just looks really great.

Strongest Aeon
Name: Yojimbo
Why?: Simply because if you manage to use Zanmato, it instantly kills ANYTHING(correct me if i'm wrong), so he is the hardest.

My Fav Aeon
Name: Bahamut
Why?: Simply everything about him is really great, he looks so strong and is generally cool.