This is kinda a thought question and you will get biased responses but here we go.
First off it really dosn't matter what you think you want unless you want to be an MM. Nearly everyone in your grad group will put the same thing on the list ET then EM then MM since MM makes up over 50% of the comunity there are mostly disapointed people. Here is the kicker I makes little to no differance how qualified you are for any of the three ratings. Yes if you score terible in the elec section of the ASVAB you will not get selected as an ET or EM but... the selection is done by division in relation to the number of that division in the grad group... ergo if you are one of the hightest numbers in your grad group (excluding 900 companies) they you are almost certain to get MM, why? because the selection is based on three things. First needs of the Navy (you will here this many times in your career) second your ASVAB scores, third what number your division is in your grad group (you will have next to know idea what that is unless you are the division YN) Last your personal choice.
There is a lot of info on what the various rates do in their early career, but what most won't talk about is once you get to the later parts of your career there is little differance between the "4" rates. But here is the short and diry for the first sea tour (surface)
MM= hardest, long working hours, no respect, no reprive, no air conditioned watch to look forward to, grease, grime, and tubine driven fire pump maintenance.
ET= hard NUBS clean all the time and do no maintenance but you have Rx Techniciton watch to look forward to (if you kiss the right booty)
EM= some hard maintenance, leave early, overmanned, less watch, get to complain about taking M and RM watches since they have no people to stand them, overall the easiest rate
ELT= work hard to get qualified since you have to go to the CO for ELT, qualify some MM watches just to placate the system but never stand them except for proficantcy (once a month), only reason they are not the easiest rate is to get this choice life you must risk being in M-div.