The chassis is virtually the same, apart from the addition of USB-C and a relocating of the wrist strap holes to the top. I actually use the official Sony CP1 case on my A5 Quaderno Gen 2 just because I happened to find that case on clearance. The main improvements are speed-related, screen related (noticeably better contrast) and most of all, a dramatic improvement in pen feel, speed and accuracy. Also some nice functionality improvements, especially around the highlighting function. There's also now a freehand highlighter.