The speedy damier answers to a large demand. I've once asked for it to the LV staff but they answer me that it was only available for a special order. Now it is a real luck that it is available! So, I have bought the monogram with regrets because damier is much more sober (and in France there is so many ugly fake monogram's). Now I would like to buy my speedy in Epi leather because it is so chic. To answer to your question , if your want something more casual that matches with a lot of clothes and accessoiries choose DAMIER. If your want something more sophisticated choose the EPI Speedy but whatever you choose, Speedy is a very good value. A beautiful bag and very functional. It is a secret for nobody that it is the best seller of the Maison LV.
I would choose the damier!!! I like it much more than the epi... but I would be weary and would need to MAKE SURE the lining on mine doesnt bleed as some purse forumers have had problems with that. *shudders in fear*