there is a slight explanation. a no name cheapo may have shotty screws or some pieces may just not fit right.
a gotoh, or something thats a bit more for example will have a better fit.
SOME people believe that a thicker, bigger trem block produces more sustain. I THINK ITS A LOAD OF .......
but its just an opinion.
as far as a strat bridge.
well, in reality, the saddles are what matter. just as long as the screws for the saddles are tip top and not bored out, rusted out whatever then the rest is just preference. i do howevver prefer the feel of a 2 point trem to a traditional 5 screw knife style. but thats just me.