In case you've never used Office for Mac, it's not simply a clone of the PC version. It's made by a separate development team at Microsoft. It's look and feel is somewhat different from Office for the PC, and it actually has features that Office 2003 for the PC doesn't. It all depends on which one you like better.
I have Office 2004 running on my Intel iMac and it's actually very usable running under Rosetta. I mean, how fast do you really need an office suite to perform?
If you decide to run Office on Windows, what you might want to look into is purchasing Parallels. That way you won't have to reboot each time you want to use Windows.