Also we are replacing the French door and that window with one big sliding door. And we are also doing them all in black color.

So casement has more issues? Good to know.

If you are in a hurricane zone I’d prefer a casement. In my opinion they seal much better than sliders.

I’m in San Diego. No (real) hurricanes.

What brand and line of windows? Many brands the slider is the low end of their product offerings.

Simonton

Some good feedback above.

Casements: Best seal, higher end look (subjectively speaking), more service issues (they sag), higher cost.

Sliders: More glass, less money, they don't seal as well and can have some install related issues when the outer edge of the sill isn't fully supported.

Based on being in a pretty mild climate, I'd say that sliders would be a fine option for you.

"So casement has more issues? Good to know."

That is not right. I think the comment above to "more issues" was referring to the screens having more issues not the casements themselves.

Tell us more about your "window guy", specifically what brand of windows is he talking about? All this discussion of casements vs sliders is not that meaningful if we are talking about a low-end brand vs a high-quality brand.

I've actually never had a windows contractor recommend sliders instead of casements. The sliders have so much air infiltration compared to casements. But as HomeSealed mentioned, perhaps in a mild climate it does not matter as much. In my climate it matters a great deal.

The brand is Simonton. Thank you for your advice!