Oddly enough there appears to be a significant sizing difference between La Sportive rock shoes and mountaineering boots.
Specifically in width.
I have a wide forefoot. With most lightweight shoes (sneakers, daily wear shoes), I wear out the outside toe first.
I cannot wear La Sportiva boots. They are noticeably tighter in width when sized properly in length.
Yet La Sportive climbing shoes fit me very well.
I find Scarpa mountaineering boots are a perfect fit but their approach shoes are tight. I wear a "true" size Scarpa boot and a 1/2 size large Scarpa approach shoe.
So I've got Scarpa mt boots and La Sportiva climbing shoes.
I'm guessing La Sportiva boots and shoes are made in different factories or even countries.