If I am right, I have read somewhere that the Briggs Vanguard is a very good engine and not like all thoe other Brigg engines. If that is true then I would say that both machines that you have been checking out have good engines (I like Kawi engines).
The most important is dealer support. You want a dealer close by that can serve you well if you have problems with your machine. Next, check to see which one has the best drives and the best warranty. Finnaly, if you can, try them out to see which one you like.
Personnaly, I would say that both are good mowers. It all depends on personnal preference. Ferris does have a nice suspension for a smooth ride, but you have to get use to not "flooring it" when starting from a stop. Otherwise it won't cut well (deck will rise).