RIght binding size for boots

Hello, I have Adidas Samba 11, small footprint at least at the heel.
I have to decide in between Nitro team M or L.
M seems too short (although I could adjust Heel 1cm) but L seems too wide at the heel. Any advice? here pics of heel in medium and large and lenght in medium and large.
According to Nitro size M goes up to 10.5 boot, however 10.5 and 11 boots have IDENTICAL width in Samba at the heel and only differs in lenght, 5mm.
These are my first boots and bindings and I have not idea if heel should be snug or not… maybe should I trade those bindings for another brand?

I would look at any Now bindings in size large that have Hanger 1.0. It’s a narrower heelcup and should work well for you. Not to mention, they are fantastic bindings with great board feel and performance.