Question: In Windows 8, is there a difference between:

*Shutting down* my computer (inside W8) and then instantly *turn it back on* again  

**vs.**  

*Restarting* it from inside Windows 8

Edit: Talking about normal Windows 8 desktop (not RT).  

Edit2: Reason for asking is that shutting down and turning on my computer did not fix something where I needed a reboot, but a *Restart* did. I've heard that when shutting down the kernel is hibernated, but not when doing a restart.

What are the implications of doing one instead of another. When do I *need* to do one instead of the other?

Answer: 
Yes, there is a difference.

Shutdown will place the kernel in a "hybrid hybernation" mode, so it won't be loaded fully on the next boot, and you will have a faster boot.
The fast start up setting doesn't apply to Restart. but what is fast start up? you can see below link for detail information about a windows 8 technology called Fast Start up (aka: hybrid boot or hybrid Shutdown) 

[Delivering fast boot times in Windows 8](http://blogs.msdn.com/b/b8/archive/2011/09/08/delivering-fast-boot-times-in-windows-8.aspx)

but how to disable it, simply if you disable hypernation hybrid bood has been disabled and startup, restart shutdown works like windows 7:

1 - Open an Elevated Command Prompt.

2 - In the elevated command prompt, type: 

> 
> powercfg -h off
> 
> 
> 

and press Enter.

3 - Close the elevated command prompt.

4 - restart windows.