as the title says I would like to know if windows 8 is any better to use for development than windows 7
I personally see no “real” difference between them -> it runs perfectly on both 
More opinions:
https://forums.unrealengine/showthread.php?6537-UE4-performance-on-Windows-7-vs-8
I use Windows 8.1 now, but have also used UE4 with Windows 7. There really isn’t any difference, both work great!
IIRC there will be no DX12 support in Windows 7, thus forward looking choice is Windows 8 atm.
Windows 8.1 + Start8 and ModernMix by Stardock, is what I find best…
Get Windows 8.1 to be future-proofed a bit better.
Windows 8 vs Windows 7 in terms of Unreal Engine 4? Not much difference right now as far as I know. I run 8.1 and it works beautifully.
I’m actually amazed by how little tweaking I have to do to get Windows 8 to be as I like it. Sure the tweaks are more drastic, effectively removing the Start Screen, but I only install four or five tweaks on 8.1, as opposed to probably 10-12 on Windows 7. Start8 or one of the free equivalents is a must, ModernMix is nice to have if you use modern apps at all. (I just use the default PDF reader.)
The nicer task manager and file explorer in Windows 8 are invaluable. Explorer in 8 even beats Teracopy in my opinion, and the task manager is far nicer than any of the alternative task managers I’ve tried through the years. Both of those are likely to be relevant as you develop, so they’re likely worth it.
If you use multiple monitors (If you’re wanting to develop, especially games, you should) then Windows 8 has far better native support. Since the best third party option seems to be $40, I’d say that’s a fair price.
In other words, 8 is no different from 7 specifically for Unreal. But I think it’s a better operating system, and I’d suggest you use it anyway.