Yes—if you are planning to sit for more than about 20 or 30 minutes, a park bench with a back is almost always the more comfortable choice. The main reason is simple: a backrest gives your spine somewhere to rest. When you sit on a backless bench, your lower back and core muscles have to work continuously to keep you upright. That is fine for a short break, but over time most people start to slouch, and that slouch transfers extra pressure to the lumbar discs and hips.
That said, not all backed benches are equally comfortable. The angle of the backrest matters a lot. A slight recline—somewhere around 100 to 110 degrees—feels much better than a completely vertical board. A contoured or slatted back that follows the natural curve of the spine can make a big difference too. If the backrest is too low, too hard, or set at an awkward angle, a backed bench can still become uncomfortable after a while, though usually less so than a backless one.
Backless benches do have their own advantages. They let you sit from either side, they tend to look lighter and more modern, and they can feel cooler in hot weather because air circulates around your back. They are also perfectly fine for short, active uses—tying a shoe, eating a snack, waiting for a bus. But for long sitting, such as reading, working outdoors, people-watching for an hour, or recovering during a long walk, the lack of back support becomes tiring quickly. Many people unconsciously lean forward, round their shoulders, or perch on the edge, which can cause neck and shoulder tension.
For older adults, pregnant people, or anyone with lower back pain, a bench with a back is clearly the better option. The support helps maintain a more neutral posture and reduces the muscular effort required to sit. If you are choosing or designing outdoor seating in a park, a backed bench with a slight recline, a seat height around 45–50 cm, and a depth around 40–50 cm will generally be the most comfortable for the widest range of people.
So the short answer is yes: park benches with backs offer more comfort for long sitting. If you only have a backless option and know you will be there a while, bring a cushion or position yourself near a tree or wall you can lean against. But where possible, choose the bench with a back—your spine will thank you.