I'm 5'6 (that's 171 cm) and I liked the 25 on me better (I thought it looked more chic and cute), although I can see how the 30 would be more practical. Saw in an earlier thread that somone described the 30 as "luggage-like" which I think is true, after all it was modelled as a mini keep-all.
Can some kind soul (with both 30 and 25) solve this once and for all for all of us here and post a picture with you holding a 25 on one hand and 30 on the other, with your height?
Looking forward to seein all you Sppedy pple out there!