I use several vendors. Usually it's Amazon, 4 Wheel Parts and Quadratec.
I have a local 4 Wheel Parts and our club gets a discount from them. Quadratec sometimes beats them, sometimes not. I have bought things from Quadratec with forum discounts many times. Sometimes I wait for Rick, sometimes I just call on.
I like my local 4 Wheel Parts as I can talk to someone, usually touch and feel the stuff and the shop guys are willing to give me advice and even loan speciality tools. The club discount is between 6% and 15% depending on the items.
What they have over Quadratec is the ability to customize. When I went shopping to rebuild my JK after my flop, I asked for quotes from Quadratec, Extreme Terrain, East Coast Gear Supply and my local 4WP. Extreme Terrain couldn't be bothered to respond, Quadratec couldn't do a customized axle, would not quote a roll cage but was competitive on many repair parts except the half doors. Factory Mopar Parts had half doors and uppers priced with shipping at a killer price, 4WP quoted the cage at a 20% discount, quoted me a custom axle to my specs built and delivered in 2 weeks for less than East Coast for a lesser axle with a 60-90 day delivery.
So, here, Extreme Terrain lost a $8K sale, Quadratec got the repair parts, Factory Mopar Parts got the half doors and 4 Wheel Parts got the cage and the axle plus the steering parts I needed after to finish the install.