Of the two units, they will both power the same items. You would appreciate both the Generac and the Honda. Both have full pressure lube engines and both are top in their class.
The Honda has a great voltage regulator system and an even better engine governing system. It also has a reputation as being the quietest. It is also the priciest unit.
With the Generac XP you get the best they offer in a portable model. It does give you 1000 watts more power and is priced $1900 less than the Honda. Generacs go-to-market strategy is to be the best value in side by side comparisons. $1900 bucks is hard to argue with.
If it were me, I'd go Generac. If we were talking 5-6kw models and price wasn't an issue - I'd say Honda. I just think Generac brings more to the party in this size range.