Hey there, just giving my two cents on this! I have been using and Intuos Touch 5 Medium for digital sculpting in Zbrush and its been perfect along side using a my keyboard for hotkeys!
I have used a small Intuos for work before and it worked out just as well, but given your laptop screen size i think the small may feel more comfortable.
Either way ive found after using it enough, you adjust to what you are using.
It may be a case of weighing up the price difference and working space you have with your laptop as either tablet would work great i think.
Hopefully this is helpful!