Well, in my case, my real waist size is 32 but I have to buy at least 34w on all my pants and trousers (jeans, chinos, flannel, wool, whatever...) and sometimes a 36w depending on the cut/shape of the pants in question, so my quads and butt can fit normally.
My jacket size is a 42 so go figure. I have bought 42 suits on SuSu and the trousers were, honestly, like compression pants I wear to work out. Extremely tight. But a size 44 jacket won't do either, too many details to fix on that one... so I just opted to not buy suits from them, sadly.
I am somewhat similar...My jacket size is typically a 44L but in pants is where I have the issue. I generally have to buy a size 40 in SS separates and get them tailored down to a 35-36 in the waist just so it can fit my thighs which are about 27inches while sitting.