I recently did a lot of research on harnesses - I am equally, if not more concerned about safety on the street than on the track, so wanted something that would be great for street driving as well, which was the driving factor for my decision. I decided on the Schroth Profi II 4 pt ASM FE harness, with the sub strap attachment. The plan is to wear the 4 pt harness on the street, and then add in the substrap to make it a 6 pt when on track.
This way, I'm covered with a 6 pt harness on the track, and I have a harness for the street that:
Is street legal (the FE cam lock makes this so). Probably not a big deal, but I don't want to give any over-zealous policeman around here an excuse to write me a ticket
Is easy to put on - I don't have to put on the sub strap every time I want to hop in the car
Most importantly, provides protection against both submarining and neck injury. I am concerned about a 4 pt harness making neck injury on the street more likely compared to a 3 pt harness (since your torso is more restrained with a 4 pt), but the ASM component (piece of the shoulder belt that gives way in a crash, allowing one side of your torso to twist forward) helps with this by allowing your torso to move in the event of an accident, reducing stress on the neck.