The online whorehouses offer one thing: better price
There is literally zero customer service regarding product selection, choice, etc. That said, greenfarmparts has about the best pricing, but don't forget to use the appropriate coupon code.
I wouldn't mind giving my local dealer my business if he'd do a decent price, but what you will find is that you can get the stuff for around 5% off and then if the order is large enough another 6% plus the sales tax savings...