Latitude E4600 versus Percision M2400

Can somone please tell me the differences (quality of build, etc) between the two? I don't really need all the higher specs of the M2400 but more is always better. What about the heat difference of having a faster CPU & GPU? I'm trying to cover all bases before I make my order. Thank you all for taking the time to reply to someone who wants to make the right choice the 1st time.