3bet adds more pressure because your making them put in more money then what they inititally intended and works if the opponent isnt good enough to 4bet you
the reason it works is if they arent good enough to 4bet they usually dont have a plan set when they miss, as a result your cbet takes it most of the time
The way the check raise works is, you let them see smaller flops, so your controlling the size of the pot allowing them to raise but then you are having to put more in before you know where you stand, if he has missed you usually take it there and then but its only a small pot, but when they have hit you lose a slightly bigger pot given your raise sizing is correct
i guess stack sizing is the key element in all of this, if you have 15-25BB your check raise might be better, but when you are deep stacked like at the start your 3bet is always going to be better
Other issues with the 3bet is, unless your in position, and opponent gives certain
tells as to when he hits or misses, then your purely check raising in the dark, and do this too often then opponents will start to fight back, in which case you have to hope you hit a big hand at the same time they do chose to fight back