DerekS got my vote, and would have even if T had been in the poll. But he'd definitely have been my second choice!
My thought, mentioned upthread, that pocket handkerchiefs were difficult to integrate into this challenge's outfits, is only reinforced by seeing many of the entries. I'm not really a fan of even the white linen of Derek's fit, but everything else about his fit works so well that it's fine in context. It's just really difficult to find a square that works well with the harsh contrast of red & white, especially when one throws in two more colours in the jacket & trousers. Crusty & Aravenel would have been contenders for my vote if they'd had different - or no - squares. And RDiaz, Sharply Tailored & Thin White Duke all had outfits that would have been improved with other (or no) squares. sb's works reasonably though, and stitchy looks just fine without one. Those two are tied for third IMO. I like unbel's fun look, but didn't really feel it met the challenge criteria.
Very interesting contest theme, stitchy. Nice one.