Yes, the small boy is definitely cuter. And looks better cross body in my opinion. I ended up taking home the old medium (and still wear it cross body at times) because it fits more. I'm the type of girl who likes to bring a little water bottle, card case, lip balm, keys, and still fit a thin cardigan in there. I'm not sure if the 3x4 notepad would fit in a small!
The height of my old medium boy is around 4 inches (measured from the inside compartment), hope that helps!
Is the old medium boy similar in size to the medium diorama? Sorry, I've never seen these bags IRL lol. I'm surprised that a water bottle AND cardigan fit!