I would say they are both overkill to be honest. I have built a system with the sabertooth 990fx R2 and it is a solid board. I would go with one of these if you want allot of features for a more reasonable price.
The Sabertooth is no better, if not worse at overclocking than the Crosshair. They're probably pretty even in 80% of OCing situations, but I find the real benefit of ROG is LN2 benching and OCing.
I'd personally go with a Gigabyte UD5 990FX; it's an incredibly solid board, without the gimmicks of ROG for your gaming needs, and without the gimmicks of the Sabertooth for your Vishera CPU that doesn't have PCIe 3.0 or any need for "tuf" parts.
I would vote for the Crosshair. There are a ton of feature on this board to really help with OCing (extra 4 pin cpu power supply, ez-plug (gives more power to pci-e slots), high quality components, etc. It is marketed towards the gaming market (republic of gamers) BUT the board is also (in my opinion) the best option for overclocking. The sabertooth is great for overall system stability, but if you really want to push your system ROG will be better. There are however many other, cheaper options that will probably give you what you want. Unless you're looking to really push a system (5ghz on the cpu, multi-gpu set up, for example) I would recommend the sabertooth or the gigabyte previously mentioned.
Between the Sabertooth & CHV-Z go with whichever one you think looks better/want more. They both use the same UEFI albeit CHV-Z has a few more hardware level bells & whistles (LN2, intel NIC, soundcard, buttons, etc). Both are solid boards all around for overclocking and taking a punishment. The Gigabyte UD5 is pretty good too if you want something else to compare with which will deliver overclocking features & good looks. The MSI GD80v2 works well too (I have it) but lacks the immense tweaking functionality that my older Asus board had in regards to memory timings/drive and your VRM control. It shouldn't really matter unless you get deep into overclocking. I also think that Asus has the best motherboard software out of any vendor (I actually used the stuff and it worked well + didn't look like ass).
TL;DR get whichever one you like more, they'll all deliver the same for what you're looking out of a motherboard.
Thanks for your inputs i have a different setup in mind for each board and mostly cosmetic(gold&white or red&black) with the best components i can buy. At the moment I'm leaning towards the Sabertooth for the aesthetic pleasure. But for the long run i don't want to miss out on the extras the CrosshairV F-Z has like the SupremeFX III. Probably a minor point but if i can get the same performance with the Saber i really dont need to spend a extra £40...
Really enjoy the quickness of it, at the moment I'v used the Mobo OC tuner and overclocked the GTX 770, now I'm reading on how to overclock the CPU further. I'm very happy with the aesthetics of the build too.
The gen3 are no longer in production you wont be able to find one new, also the only difference I read about the r2.0 gen3 was there were PCIe 3.0(sabertooth r2.0 has PCIe 2.0) and as for now no graphics cards are able to take the full advantage of it. Someone correct me if I'm wrong.