Scott Scooter Sowle wrote an answer about La Sportiva Xplorer Shoe - Men's on August 26, 2014
I've been in La Sportiva boots and approach shoes for a few years and wear a 10.5 street shoe, I would suggest the size 44. For approaches wearing a SmartWool Trekking or Medium Hiking socks will provide more padding and comfort. A suggestion is to get a 44 and a 44.5 try them on with your approach socks and keep the pair that feel the best and send the other pair back with free return shipping. Call a Backcountry.com Gearhead and they'll help you out with this and I'm sure you'll be happy with the outcome.
Meanwhile get out and enjoy the Backcountry!