Regarding lenses, I think you're referring to the shutter. Of course a new shutter is better than an old shutter, but there are plenty of old shutters that are quite servicable. Most of my lenses are in older shutters.
An F has the swing/tilt calculator on the side of the rear standard. The F1 has a drum mechanism so the calculator is readable directly from the back of the camera. The F2 adds micrometer focusing on the front standard, while the earlier models only have geared focus on the rear standard, and the front standard is more robust. The differences in functionality are small, but the F2 is more expensive, since it is a current model. Parts are largely interchangeable, so it's not unusual to find Sinars with mixed and matched parts, like a camera with two F1 rear standards (one on the front).
An F has the swing/tilt calculator on the side of the rear standard. The F1 has a drum mechanism so the calculator is readable directly from the back of the camera. The F2 adds micrometer focusing on the front standard, while the earlier models only have geared focus on the rear standard, and the front standard is more robust. The differences in functionality are small, but the F2 is more expensive, since it is a current model. Parts are largely interchangeable, so it's not unusual to find Sinars with mixed and matched parts, like a camera with two F1 rear standards (one on the front).