Beginner: Should I get the Speedy 25 or 30???

Soo0o0o...I bought the 30 and thought it was a bit too small...so I brought it back and got the 35 and now I feel like it's a bit too big!
what should I do? Take it back...again... get the 30?
 
i have both sizes and find I use the 25 more. i don't like to use the 30 unless I have a ton of stuff to carry around, I find it sags and just looks goofy. now the MC 30 I love love, the leather is stiff and does not loose its shape which I like
 
I have both 25 & 30 in mono and a 25 in Damier. I agree about having both sizes. I like the 30 when I'm carrying more, still love the 25 too. I carry a mono zippy wallet, small agenda, cell phone, makeup case, kleenex, pomme 4 key holder and other miscellaneous things. Both sizes hold a lot. The 30 does sag more but I like it for trips when I might want to stuff a lot in it.