Parallel clamps are the result of hundreds of years of research into developing a clamp even less intuitive than handscrews. I love 'em, but man are they a hassle when the head doesn't engage the bar.

Pipe clamps are comparatively cheaper with the bonus that if you need longer clamps, you can go to the plumbing supply for a longer bit of pipe. They aren't as nice as parallel clamps for gluing up thin panels though.

For handscrews, I highly recommend Miro Moose. The Besseys are surprisingly subpar. Lie-Nielsen makes them as well for a reasonable price, but they galvanize the screws, and I don't like the action as much.