Smith's are lighter than Costas with glass lenses but in my experience the Costa lenses are still better quality. And for a large noggin like mine, I've found Costas fit me better than Smiths.
If you're spending any time on the water and need polarized lenses, Costas & Smith are the only ones you should consider.
Maui Jim haven't been on the level of Costa & Smith for a while. They're for golf bros and people who want to look like they spend time on the water.
I've had 4 warranty claims with Costa both before and after they were bought by Luxxotica and no issues whatsoever. And they've been for similar issues every time- the most common one is the delamination of the rubber pieces at the nose and temple. This is a universal problem with all brands. The combination of oil and chemicals found in our sweat, skin, and sunscreen all break down the glue to that holds the silicone/rubber to the frame. I've had Costa replace a pair for this and just repair a pair. Also had the earpiece snap- once they replaced with new glasses and once they simply repaired it.
In each instance I think I paid a small fee or maybe just shipping.
I don't know what you people are doing to have such problems with the warranty process.