It really depends..on your frame and how you choose to wear it. When I bought mine, I went to the boutique convinced I would get the 30. But when I tried it on crossbody, which is my preference, it looked like a duffle bag on me. The 25 was just right for me! Some don't like the smaller opening, but I have small hands and invested in an organizer for easy access, too.
I debated constantly between the 25 and 30 before i got my mono....went with the 25 and love it...So i bought DE in the 25 too...i have a black MC in the 30 and its so much bigger.....i do much prefer the 25....i think you could wear either with your height, so The real question is how much room do you need? Do you carry a lot of stuff? The 25 will fit a fair amount but if you use a bag organizer it won’t fit as much. And, do you intend to wear it crossbody? Vs shoulder or arm carry....imo, the 30 looks bulky when worn crossbody....but some like it that way, so its really personal preference.