I like Amazon due to the speed, reliability & easy searching of their site. I tend to buy a most stuff from them these days with the free Amazon Prime 2 day shipping. Somehow I don't think tractor implements would fit under the Amazon Prime program though (unless you go the often used Ebay route & just jack up the prices more than shipping could be & claim free shipping).
One of my biggest annoyances searching for tractor stuff is prices aren't posted. A lot of dealers advertise the brands & types of equipment they sell, some actually list out particular models of stuff, few actually have prices posted for the stuff. For me, one of the draws of everythingattachments is I can go browse their site & it's trivial to figure out what they sell, a good amount of details about it & how much it will cost. I get annoyed if I have to call up the dealer for every little thing, I don't want to have to do that when I'm researching or dreaming. Direct dealer contact has it's value, but I like other options as well.
I like being able to research the snot out of stuff I may or may not end up buying. Amazon might be able to facilitate that a bit more.