i'm going to say Damier speedy 25/30 OR Mono speedy 25/30... both these bags are great!!! well i havent seen the Damier speedy yet, but i think it will be beautiful! as for the sizing... it just really depends on how much stuff you carry! i've got a Monogram 30 and its perfect!
good luck on what you decide!!! and WELCOME to the PF!