Ive been looking at harnesses for my self. I decided on CROW. They are one of the cheapest, they meet most of the different race car harness restrictions (like nascar and trac stuff), they have all the accesories available, and are easy to find. A lot of the other brands your just paying for a name.
Personally I am not going w/ a cam lock because Ive heard if you get them dirty they jam up (w/ no roof on the xj there gunna get dirty) and some say they dont release under pressure, aka when your upside down and hanging.
the 5th point keeps you more secure, it keeps your ass in the seat, keeps the lap belt from riding up. Personally I never thought Id like 5 point belts, but after riding in 2 JeepSpeed rigs 1 with 4 and 1 with 5, I like the 5 better and now understand why its there.