The same goes for a great many things. Walk in to the Woolworths in Scottsdale (Tas) and you are greeted by a genuinely friendly person. Woolworths in Port Augusta made me think they'd put a knife in our back as soon as look at us.
Nissan's no better and even the one dealership can change. My own dealer has a guy that works in the service department who really knows his stuff quite well, but the current service manager is a useless prick - the previous guy was far better to deal with.
Ringing around is always a good idea, so is shopping on the internet, but seeing something in the flesh is always rewarding and often mind-changing. Problem is the salespeople can influence the decisions - so sometimes it's best not to tell them too much at all, or listen to them too much, because as Krafty noted, they will push the more expensive items towards you. Particularly if the sales person has a commission, or a vested interest in the store's nett profit.