I think the 30 is still more popular but 35 is slowly becoming popular! A year ago I thought the 35 was huge and the Galliera GM was way too big.
But after carrying my Galliera PM's and then going back to my 30's--they just seemed too small. I ended up selling my 30's to get 35's and I'm so happy. I think if you're very slim- size 2/4 or under, or petite and slim (under 5'4") with heels on--sorry gotta count those heels!-the 35 may overtake your frame.
I'm 5'6" without shoes on and slim/average and the 35 looks good on my frame. The 30 looks good too but I like the larger opening of the 35- I can easily see all my stuff and things are not piled on top of each other.