I've had both Yamaha and Honda. You really can't go wrong with either one.
The Yamaha has shaft drive as well. The Yamaha will be more 'trail friendly'. Both will be work horses, the Yam has a bigger motor and will just as well for work type stuff. If you need an EFI there is only one option between the bikes listed. I have had one EFI machine and it wasn't as cracked up to be as they made it sound.
That said, I now have a honda foreman 450 but bought it because of the deal. I'd trade it for a Yamaha Grizz 450 in a second if I had the $ for the Griz.
