My friend, I've got you covered. Based on the talk in here I got all hot and bothered yesterday and ordered the shoes from a local spot, and lo and behold they showed up today via courier. I think I'm going to send them back, though, and stick with the Mizunos and my Asics for now.
The Diadoras have that thing that really bothers me in so many shoes these days, the 'funneling' effect of the toes, as if I were an elf. One of the commenters of the clay version on tennis warehouse customer feedback mentioned Diadora changing the toebox angle on this version, sharpening it, which worried me, and sure enough I found this to be irksome with my foot. Wearing them around I can tell that this isn't quite as sharp as, say, the Wilson Rush Pro 3s were and maybe they'd be fine once broken in, but the last couple of toes are in fact getting run into by the angle of the shoe (big toe and second toe, meanwhile, have plenty of room).
Maybe this would break in and be totally fine in play, but I don't think I'm willing to find out at this point. Might return and maybe snag these later on if they're on a sale, or perhaps the Fly version. Anyway, I've made some pics to illustrate what I'm talking about. As you'll see, the Mizunos I like because it's a much straighter last, the toebox more rounded out rather than sharply inward. The Asics Speeds, which I added in the second pic, are directly in between the two as far as the toebox angle thing is concerned, with the Diardora having the sharpest inward tilt.
Which brings me to your sizing question: pictured are a
Mizuno 44, which they call a US 10.5, beside the
Diadora 43, which they call a US 9.5 (The Diadora '44' is a 10 and the Mizuno 44 is a 10.5 - these companies are drunk). As you can see, length wise the Mizuno US 10.5 is just barely longer than the Diadora US 9.5. I was ideally a 9.5 US in the SCB and a 10.5 in these Mizunos. If you were a 9 in the SCB, then I think the 9.5 Mizunos may be your sweet spot but if possible I would just order both a 9.5 and a 10 for an at home try on to see which fits you best and send back the other.
Pics below. Paper towel is there to protect the dirt from the floor because as you can see the Mizunos are caked with clay. Lined them up at the heel with the help of the racquet to best get the proper judge of length. Last pic is of the two shoes on my feet.
Diadoras do feel nice, however there is slight heel slippage in the heel so I'd have to go to the second eyelet and maybe even a runner's loop. Mizunos are actually more secure in the heel with just the first eyelet, no coming up out of the shoe, I think because they're not as wide there in the opening.