actually every body at starting has this confusion, dont worry, in learning process !st you should 1st get confidence on learning process, that may be possible, by getting work regularly with any basic controller like Arduino, my suggestion is, start with Arduino, why because, Arduino is open source and lot of libraries already available, after getting some confidence and femiliarity with controllers u can learn any microcontroleer u r own easily, After Arduino go through 8051 micro controller in Engineers garage good stuff is there to learn 8051. that is enough to learn sufficiently.