Here's the best I can help.
These will fit a lot of different ways. That's not a cop out but if you rock your kicks unlaced and loose then you should go down a half size.
I wear a 12 in Jordan IV, it's loose but doesn't slip.
in Jordan III, slightly more snug than 4 but not tight.
in Asics GLIII I tried an 11,5 and kit was too snug from the start so I'm def a 12 there.
As far as Jordans I'd say these are closest to the VI.
Now for just reebok,..
All of my questions are 12s but they're on the tip of being too loose.
My answer 4s are 12s and fit great.
The Kamikazes IIs I got I've gotta lace up. I actually don't mind cuz I feel like the shoe isn't really that chunky too look good loose anyways. But when I loosed the laces my heel was slipping out the back which is pretty much like my VIs maybe a lil worse cuz I feel like the heel shape makes it easier in the Kamikaze II. After I laced 'em up they fit great as the collar really holds you in when you use it. Since I like to rock mine loose if I get the sonics raindrops I'll prolly try on an 11.5 loose before I grab another 12 just to see if it makes a difference.
Everybody's feets are different tho so I hope that helps. I've got high arches and a normal width in the toes.