Maybe that vent hole is what causes the Schmidts to fail if they get drenched. I'm not really a Shimano advocate, I would prefer to have Schmidts, but Shimano dynohubs have treated me very well over many miles. Some of those miles under extreme weather.
I view a warranty on a hub as fairly unimportant since you can't mail them the wheel. Even if you could, it's expensive. So getting warranty work done costs me a minimum of $100 to rebuild the wheel, and probably more since I don't like to re-use rims. I've heard of people getting warranty service on Schmidts, no so on Shimano hubs. When it would cause me difficulty, I ride with a backup light, but I don't expect my Shimano hubs to fail.
A long time ago someone pointed out that the manufacturers price warranties into their products. If they don't think they will have any costs, they will not put much of a price premium on the warranty.