Older pieces have coil springs and hardwood frames that are doweled and glued; today’s pieces have rubber straps or zigzag coils instead of spring coils, and staples are used on frames.
The same goes for the height. If you’re short, buying a sofa with a high seat height or a large seat depth means that your legs will dangle. This ultimately puts stress for your core and lower back as gravity pulls your feet towards the ground. On the other hand, if you are tall and the sofa is too short/has shallow seating, you might put undue pressure on your knees.