What I've noticed on Windows 7 64bit SP1 is that is uses a lot of resources while syncing.
I don't have this problem on Ubuntu 14.04
In both cases I used the QT wallet.
You point out something I noticed with several coin wallets that I use, that they don't run as efficiently in Windows as they do on Linux.
I don't think it is particularly a Windows issue, I believe it is linked to the libraries used in the compiling are not Windows optimized. If anyone has some insight on this it would be greatly appreciated, so that new releases could benefit from better performance on Windows.