I say buy whatever you're comfortable with. If one sticks to a particular make/model/part, there won't be that much difference.
It's like helmets, if you're shopping for a Shoei X-11 no matter where you go most of them are going to be older helmets that have already experienced some degree of foam degrade. If you are looking for a good deal on Bridgestone BT-02s, they may have some "shelf wear" on them as they too haven't been manufactured in a while.
I know riders in Texas who pickup tires at great prices, store them, and look for a shop to put them on when needed. A lot of shops there will do this, but most won't where I live. Shops that do work on cruisers more often tend to be more appreciative of those that work on sportbikes. A shop that sells a lot of smaller bikes usually sees their customers bring in the wheel only for tire replacement.
Tire Sales and Replacement is big business for shops. It's an opportunity to have a customer's motorcycle actually in their shop represents an opportunity to check a bike for possible warranty work, suggest repairs, and offer upgrades. A customer bringing in a tire can also represent an opportunity, but it's difficult when the customer's bike isn't there. A few dealers in my area will even pickup a customer's bike, rather than encourage them to "bring in the wheel".
What should be avoided is general offers, especially if you are sensitive to premature tire wear. Tires don't last forever, and age even when they aren't mounted. Find a tire that you like and stick to it; that will help ensure that you're not falling for a low-price offer that isn't for you. For example; I like Bridgestone Battlax and Dunlop Qualifiers; and don't go for anything else.