Re: bathroom exhaust fan vent
I disagree with roof venting being the better option --- it lends itself to other issues -- besides if you get discoloration on the siding you will also get it on the roof.
I'm not sure what the concern is with the exterior hood --- if it has to do with not using the louver type there are typical sloped hoods available. Whichever type you choose make sure it as a backdraft damper to prevent outside air getting into the ducting.
"" an ounce of perception -- a pound of obscure "