2TB or 3TB which is safest?

I currently have a 500gb My Book. This is now full and want to upgrade to a larger drive. I note on the board there are many people having problems with the 3TB drives. Does the same thing happen with the 2TB drives. I read somewhere on the internet, that most windows operating systems cannot cope with drives larger than 2TB. I don’t know if this is correct, but when I asked in PC World yesterday, their help desk staff suggested, you could only use a 3TB drive if you had a business edtion of Windows8. I know the old drive is now full, but don’t want to transfer to a new drive if it will subsequently freeze up and lose all my files. Any help would be appreciated. 

You can get the 2TB or 3TB model, as long as your motherboard supports that size. 

I don’t think the drive is the problem. I think it is the USB 3.0 that is the real problem especially ones using addon cards. There are a lor of things that can cause conflicts. I’ve seen Logitec devices mentioned several places as a problem. Over all I think the USB 3.0 still has plenty of bugs to work out.