Honestly, it depends on the bench. Many street benches are designed to look great in public spaces, not necessarily for long-term lounging. If you plan to sit for more than an hour, pay attention to a few things: seat material, backrest angle, armrests, and whether the slats create pressure points.
Most decorative street benches use wood or metal slats with a slight curve. They can feel fine for 20 to 30 minutes, but after an hour you may start shifting around. Wood is warmer and more forgiving than metal, but if the slats are too narrow or spaced too far apart, they can dig into your thighs. Metal benches look sleek, but they get hot in the sun, cold in the shade, and feel hard quickly.
A bench with a backrest tilted slightly back, around 100 to 110 degrees, and a seat depth of 16 to 18 inches is usually the sweet spot. If the bench is backless or too deep, you end up slouching or perching, which tires your lower back. Armrests also matter more than people expect for long sitting because they let you shift weight and stand up more easily.
So if you are asking about those stylish public benches you saw, my honest answer is: they can be comfortable for an hour or more, but only if the design supports your body. If it is a flat, backless, metal slat bench, it is better for short rests. If it has a slight recline, wide wooden slats, and armrests, you might happily sit with a coffee or a book for quite a while.
One more trick: bring a thin cushion or sit on a jacket. That small layer can turn a hard but beautiful bench into a surprisingly pleasant seat. But if the bench is more sculpture than furniture, your body will know within 20 minutes.