WD-40 is great stuff but it is not a lubricant. My old cans say "...cleans and protects", "...stops squeaks", ...displaces moisture", "loosens rusted parts". No where on my cans of WD-40 does it say "lubricates". Things may work as if they were lubricated because they were "cleaned" and "loosened". A coating of WD-40 may have some minor lubricating effect (so will water) but it certainly won't withstand stress or pressure between surfaces. Don't you suppose the WD folks would brag about its lubricating qualities if there were any???
I personally like a spray silicone for its ease of application and penetration. I suspect (no empirical proof) that the silicone is less "tacky" thus attracting/holding less dirt/grime.
Just so you know WD-40 does lubricate, because it has silicone in it. I know this because we used to use WD for general cleaning, rust prevention, as well as for lubrication at our shop. We had to discontinue use of the product because of it's silicone properties ruining our clear coat in the paint booth. Silicone becomes atomized into very small particles and floats around the air endlessly, so it would lad on a part right before the clear coat causing fish eye in the clear. We had a guy from the paint store come out and analyze the shop for contaminates including and air sample. So just so you know WD does have silicone in it, so hence it does lubricate.