tyson's defense is a variation of a peek a boo. his slipping style, uses a side bending motion. he takes his hips and shoulders and moves them in opposite directions for quick slips.
the hand up/hand down defense is called a half guard defense. its a narrow stance and leaves the head a bit vulnerable but both those points are good for drawing and slipping punches. it was used a lot by old detroit fighters but the art has been lost over the past few decades. the young fighters still try to use it but neglect a lot of the attributes needed to master it (PBF & toney are both good at it, and both from the detroit area). DLH does it wrong too. mayweather sr knows it but doesn't know how to teach it well. DLH touches his shoulder to his chin but what you want to do is raise the shoulder as high as you can to the cheek bone so you know the jaw joint is protected. there's a few more points to it but thats the main one.
it also depends on how you use it. its not a wonder defense becasue you still have to use it appropriately. for example, take a look at the fight with gatti and PBF. gatti slips the jab then stays in that position. what the hell is he staying down there for? if he slipped the jab, then raised up rolling his shoulder at the same time it would have blocked the straight right. he could then counter, or block the hook, etc etc etc. PBF uses it really well against n'dou, laughing at him the whole time he's on defense. like all skills, it takes practice. there is no one wonder defense.
"Learn the best skills and give the best effort because winning has nothing to do with luck!"