Honestly, if comfort is your main priority and you are not planning to use thick cushions, wood is usually the winner. That does not mean every wooden bench feels amazing, but wood has a natural advantage: it reacts more gently to outdoor temperatures. On a hot summer day, a metal bench can become scorching enough to burn the back of your legs. In cooler weather or shade, metal feels cold and uninviting. Plastic tends to sit somewhere in the middle, but it often flexes or feels hollow, and cheap plastic can get slippery or uncomfortably warm.
Wood, especially a smooth-sanded hardwood like teak, acacia, eucalyptus, or a well-finished pine, feels warmer to the touch because it does not conduct heat away from your body the way metal does. It also has a subtle natural grain and slight surface texture that keeps you from sticking to it when you sit in shorts. Another point is rigidity with a little give: wood does not usually flex like plastic, so it feels stable and supportive, but it is not as brutally hard and unyielding as steel or aluminum. Over a long afternoon with a drink and a book, that difference really adds up.
That said, comfort is not only about material. The shape of the seat, the angle of the backrest, and the height of the bench matter just as much. A curved wooden bench with a slight backward tilt will feel better than a perfectly flat wooden plank. A metal bench with a contoured seat and a good cushion can easily beat a poorly designed wooden bench. Plastic benches with a textured, ergonomic shape can also be comfortable for short stays, especially in coastal or poolside areas where you want something that dries fast.
If you live somewhere with extreme sun, avoid dark metal unless you plan to add cushions or place the bench in full shade. If you want low maintenance and do not mind a more casual look, plastic is practical, but it rarely feels luxurious. For the best balance of natural comfort, stable support, and outdoor durability, wood is the material I would choose again and again. Just keep it lightly maintained, and if you want extra softness, add a seat pad—but with wood, you may find you do not even need one.