What is good really is going to depend on what federation you are competiting in....do they allow all kinds of gear (shirts, squat suits, etc..) or is it a RAW association. What about drug testing? etc...that stuff all has to be taken into account.
The reason why there is an overlap between weight classes is because of guys dieting down. For example. The guys at the top of one weight class may lift just as heavy or heavier then some of the guys at the bottom (or even the middle) of the weight class above them. This is because they should really be lifting in that weight class but they may be at the lower end of it, say 5lbs away, so they just diet down those 5lbs without losing strength and they compete in the weight class lower and blow away the competition where as if they stayed in the heavier class (say the 200lbs class) they would get crushed by the guys who are dieting down from being on the boarder of the 220lb class....see what I mean?