Honestly, if pigeons are a daily reality, you want a bench finish that is smooth, non-porous, chemical-resistant, and tough enough to handle frequent washing. My top recommendation is galvanized steel with a high-quality polyester powder coat. The zinc layer prevents rust if the finish gets scratched, and the powder coat creates a hard, slick shell that bird droppings cannot soak into. You can usually hose it off, wipe it with soapy water, or even use a mild disinfectant without damaging the surface.
A very close second is thermoplastic-coated steel. This is the thick coating you often see on commercial park benches and playground equipment. It is extremely resistant to stains, moisture, and the acid in bird droppings, and it cleans beautifully with a pressure washer on a low setting.
If your budget allows, stainless steel benches are also excellent. They have no paint to stain or peel, and the surface is naturally smooth. Just keep in mind that droppings will be very visible until you wipe them, so you may need a quick daily rinse.
For a more natural look, choose high-density polyethylene or recycled plastic lumber slats. Unlike wood, HDPE is non-porous, so waste sits on top instead of soaking in. It will not rot, splinter, or need repainting, and it handles soap, bleach solutions, or pressure washing well.
What I would avoid: bare or stained wood, unpainted concrete, and rough or matte textured paint. Wood is porous and the acid in pigeon droppings can stain and eat into the finish. Concrete is also porous and grabs stains. Any matte or textured powder coat looks nice but gives droppings tiny places to grip.
So if you want the easiest possible life, choose a galvanized steel bench with a smooth polyester powder coat, or a thermoplastic-coated steel bench. Add a regular rinse schedule and it will stay presentable for years.