But if you get a good vent with a proper install, it shouldn't matter what side you put them on.
Now I have seen wind blow snow/rain issues with certain crappy static vent models. Only thing that matters is that they're installed right up at the highest point of the roof. Modern attic ventilation has nothing to do with wind. You're over thinking what side to put the vent on. But I'd want answers to those questions before proceeding with the removal of a ridge vent. Is the roofer charging you to fix the issue? Why are you buying your own vents? I'm willing to concede if it is just simply a wind blow rain/snow thing. Seen tons of mis diagnosed leaks this year on account of that. Attic rain/condensation has been a big issue this year in my region. My main questions right now are, is the ridge vent installed correctly? If so, is the leak mis-diagnosed and it's something else that is leaking? At a glance, the parts of the roof I can see look ok.
DURAFLO WEATHERPRO 75 PROFESSIONAL
But as a professional roofer for 22 years it does sound a bit fishy to be blaming it on a correctly installed ridgevent. I live up north in a heavy snow zone so we don't use much ridge vent as it get's snowed over easily blocking air flow in attics. I mean to be honest, I'm not all that experienced with ridgevent. Maybe in a hurricane or something but judging by the snow I'd guess it's not hurricane related. You're saying you had an actual roof leak caused by your ridge vent? If it's installed properly I can't imagine the insane kind of rain that would push water right up under a ridge vent.
Very curious to know exactly what the problem is.