Rigid vang
The primary advantage of a rigid vang is that is supports the boom as well as allowing you to pull it downward. You can dispense with the topping lift. Other than that, I don't see much advantage on a smaller boat.Regarding strength, there are a couple of considerations:For use as a vang, it's breaking strength should be at least twice as high as the load you're going to put on it. If you don't use a winch, you're not going to be able to put more than maybe 100 lbs of force on the vang. If you have a 4:1 purchase, that's 400 lbs of force. 1000 LB BS should be OK. If you use a cascading purchase (8:1 or other setup) or if you winch it, you need stronger components.For use as a preventer, it's a lot different. Calculate the forces of a 20kt breeze on the sail area of your mainsail. Figure out the vectors against your preventer. Add in shock loads. I'll bet you the numbers add up to a lot more than 1000lbs.