In Kyokushin it isn't allowed to punch the face. That's partially why they use that guard... For me, I don't have a specific guard, I just keep on changing them through out the fight but I always guard myself. I believe that throwing your arms down is just stupid and disrespectfull. Well, in my style of fighting, I count mostly on antecipation and dodging. As for street fighting, I do not allow anyone to come close to me. I attack first when they enter the my security circle - might look too aggresive to outsiders, but I prefer to be the one standing up in the end... I usually throw a couple of punches and then try to throw them down (while they're still recovering) and try to make sure they don't get up again... I use kicks mainly for defensive purposes, keep distance, etc. As I believe they aren't that effective and have a greater risk associated with them...