I personally like the basic guard, the sit down version when I want to rush in and the low hang guard from those pictured there
whether I use the low hang guard or the basic depends on the opponent too, like how powerful he is, how fast he is, what's his style, etc...
I generally don't like the high guard, only turn to it when it's very necessary. It blocks my vision, don't see what the opponent is about to throw and I give free space for them to lead an offense on me.
I like Philly Shell too but that's rather for people who are more advanced in boxing... Like, I can do it too but not very good yet. I do like to use my shoulder to block/parry a lot though that's a great move imo. You still have your vision, you are not squared up so it's easier to move while you are using it and you can counter more easily.