Finding a good dive shop is like finding a good instructor, it does not matter what gear they sell as in what what agency the instructor teaches, if they are good you will return.
In Dubai we lost a couple of good dive shops over the past few years having been taken over by one particular company that is well known for churning out OW divers who have no buoyancy control and swim in a vertical position. That said I still go back to one shop previously known as Scuba Dubai because they kept all the same technical staff there who service my gear, as well as fill and service my tanks etc.
It would not be the first time I have walked into their workshop and spent an hour chatting with their technical manager, a guy who is basically a walking encyclopaedia of diving. I have spent more money on new/used tanks and servicing etc than what I have bought in the main retail area.
A few days ago I was checking a shop in the UK where I will be visiting fairly soon for a ScubaPro Mk 25 DIN first stage with S600 second stage. They do not have a Mk25 with DIN fitting, so the person I was on the chat line with tried to sell me an Atomic T3 which is around three times the price, needless to say I just logged off.
I am sure some dive shops get p!ssed off when time wasters come in to try on gear and then buy online, but I am sure many of them drive customers away by not being friendly and trying to rip them off.
I have found a shop about 25 miles from where my mum lives who now have two Mk25s + S600 second stages ready for me to collect when I go over next weekend and they are throwing in two additional second stage octopus for free (although I don't need them, but I'll take them anyway), for less than the price of the first dive shop I checked.