I'm wearing UK 8 1/2 (EU 42.5) for my trusty, comfy and somewhat oversized wear-'em-all-day crest QC and UK 9 (EU 43) for the oxi s for a perfect, snug yet rather painless fit. 8 1/2 is my street size. Does this help?
I like them a lot, especially the cheap crest model. I have owned about half a dozen of them, with the grippin dura rubber. This rubber is more on the sticky, less abrasion-resistant side. According to Ocun, the new CAT rubber is more durable. Haven't been able to test that yet.
I guess the oxi s has this new rubber, but I'm not sure. Fairly sticky, not a lot of abrasion yet, but I haven't used them a lot so far.
I went to the store with the expressed intent of buying a pair of solutions and came out with a pair of oxi s. Don't know whether they can compare in terms of durability, but they sure can in terms of fit - for my feet, anyway.
The crest is my go-to model for everyday gym and rock use. They can take some punishment, perform fairly well in most routes and if you get them at 20% off it doesn't even make sense to have them resoled. They are great for smearing, suck at all sorts of hooking, and please don't try any micro edges. That's where the oxi s shines...