I had the mini before and unlike previous commenter, I couldn't wrap around my head using the bag without having some sort of worry looming at the back of my mind (bcs how open it is, the drawstring in my experience wasn't able to fully secure the opening, especially if I filled it to the brim). I guess it's also bcs I commuted with train a lot in the past. Now that I drive more, probably the mini would do just fine.
Currently have the small and it is my go-to work/ daily bag. Opening is much more secure IMO (bcs it folds) and I could manage to fit bigger stuff in dimension (A4 papers, Ipad pro, etc). It becomes a tote bag at that point and I don't mind some item sticking out.
I adore the compact size but I would suggest trying it in store with your stuff in it. I kinda notice the compact doesn't stay fold on its sides once the bag is full (from youtubers/ some posts here in PF) and tend to open up unless you secure the clasp. It probably has to do with how much you would want to carry.
Regarding the leather type, I have the soft grained and glad I went with that. My puzzles were all smooth calfskin and although the leather is as robust as the grained, I could imagine the mailability would cause structure lost in the Hammock faster, if it isn't stuffed properly (
Fashionphile is the best reference for this, as you can see clear difference through time, of how the two leathers differ in wear). I also would imagine the smooth calfskin would wear better in compact size, as there is less surface area for it to lose shape overtime.