for size 10 thirtytwo, definitely M/L.
thirtytwos aren´t especially wide, but they pack a bit of volume over the arches, making them look bulky.
My size 11 Lasheds from two seasons ago fit neatly inside my M/L datas of the same year, and the 10s are one size smaller (duh...). go M/L, as the heelcup and frame of the L/XLs will feel much too wide and in general spaceous for your boots. I had L/XL forces with thirtytwo 305s this last season, and they still felt a tad wide for my boots(then 10.5).