As stated, you'll find plenty of information regarding your questions on the site if you use the search feature or google.
I have not taken CEH training through InfoSec Institute (if that is who you are referring to). We used ISI for some internal training last year. I sat in the CISSP class and the instructor was great - making that stuff as enjoyable as it possibly could be. Many colleagues took an "ethical hacking / penetration testing" class that was supposed to prepare them for C|EH and others. To the best of my knowledge, none of them have taken any of the exams because they don't feel the course prepared them for anything. This is largely due to the instructor so ymmv.