I'm curious. On the models Military and Endura you have a male screw going into a female nut side. On models like the PM 2 and the Manix 2 you have a male screw on both sides screwing into a female bushing in the middle. My questions are.....Which is stronger? Which is more durable? Which is more longer lasting? Are they equal to each other? I guess this is an engineering question, and I'm curious if one is better in any way than the other. Thanks in advance for the help.