Setting up VMware Fusion 6: More Seamless or More Isolated option?

Best is to put it to isolated. Although Windows viruses cannot infect OS X, it'll still be residing somewhere in the Mac side, and there's a chance that you can pass it on to other Windows users.

For me, I turned off file sharing and only enabled drag and drop between OS X and Windows.

I have mine set just like yjchua95. I want to sandbox Windows as much as possible.

In regards to Windows viruses. If you had everything integrated, I would assume that if a piece of malware such as CryptoLocker infected Windows, it could find your Mac documents and begin encrypting them and hold those files ransom for your cash.

Years ago, I tried Parallels and they did everything possible to integrate Windows and it's apps to appear to work in OS X and it was extremely annoying. For example, when I right-clicked on a document, I was given all sorts of options to open it with Windows apps which I would never do. This was one of my many gripes with Parallels and I moved to Fusion partially because of how well it can sandbox VMs.