There's probably a lot of regional cultural issues here. Let me give a perspective from our side of the big pond,,,
I've bought stuff online, and I have bought stuff in the LDS'es around here. Both have their place to me. I am fortunate enough to live in a city with the first 10 dive shops, probably more (and it's not even a costal city or near any diveable waters atall!), most quite well stocked and with competent staff . That much local competition actually means that the prices are relatively fair, and so price isn't the incitament to buy online when factoring in the shipping etc.
Also, from what I understand, the local dive-shops which offer training too actually offer the training "at cost". 400 Eur for pool + confined water for an OW-training. I.e. training isn't a loss-leader for gear-sales. As a matter of fact, some shops operate as two seperate incorporated entities: a "dive school" and a "gear shop", with no financial link between them. Much more healthy, IMHO, than the "5 USD OW-course" offers you guys over there have to content with....
Anyways, back to the LDS vs. online topic.
If I want to go look for a new gizmo that fits me, I go to my LDS of choise and shop around. They let me play with things, try them on (if they're to be worn) and typically have good experiences to share. They also understand that the phrase "I'm just looking, I'll let you know if I need you" really means "I want to make up my mind on my own, and when I have you will probably get the sale if you have what I need" -- and thus avoid hard sales-tactics. If I see something I like and need, I buy it there, knowing that the price will probably be just a few % off from what I could have gotten on-line.
Stuff which is in risk of being damaged in transport, I also always pick up in the LDS -- I may pay them a little extra compared to on-line, perhaps, but then they deal with getting goods which were damaged in shipping returned etc. Fair deal, I think, since I pay for the "not having to worry" part.
But sometimes, I do just not have the time to go browse a shop for a gizmo, or the LDS doesn't have what I'm interrested in. Enter the on-line shop. Accessible from my work in the lunch-break, it's an easy and convenient way to get the stuff. They even send it to me at the office, so I do not have to be at home when the mailman comes by. Double-time-saver! My DSMB was getting worn out and needed replacement, so I ordered one, along with a few spools of line. I wanted a new pair of booties before a trip, same model as those I had, but didn't have time to go browsing LDS'es -- you get the picture, right? The on-line store fills an important spot too.
To me, it's not really an "either or". The LDS is there for instant gratification (face it, the "here and now" factor is important when you've set your heart on that new reg...right?), for helping with the tuff choises, for buffering the troubles (warranty, dealing with shipment troubles) etc., and I appreciate them for that. I gladly pay a tad more for that service -- and over the years, I have given a good deal of Eur to my favourite LDS. The online-shops are there for when I do not have time to go to the LDS, and when ordering and having delivered suffices. I am fortunate that I do not have to let "price" be determinal in the choise of online vs. local, and therefore can pick and chose based on what's convenient in a given situation.
The LDS and the online shops even compliment each other to the point that when I was trying out drysuits at the LDS and the model I had wasn't available in the size I needed, the shop-owner said "Try to get it from OnlineScubaStoreName, if you need it right away. If it doesn't fit, I'll just exchange it for you". Needless to say, I waited to have the LDS get the size I needed....