I am going through the same question just now! But i guess it really depends on what size of handbag you carry? I am torn between small and medium, but i hope my next LV visit can clearify once I get to see them side by side. If you are considering double the agenda as wallet, make sure to check out FiloFax, they have some great stuff for agendas, also i find the Agenda sub forum is very helpful too.
What agenda are you considering now? Rose Koala-cute, but not sure if i can stand the bass 'koala' being scratched from daily use, Vernis-TDF, but i can't baby it 24/7. Epi & Mono are what i am considering now, what lines of agenda are you considering?