I can't help you much in your search but I believe in WWII the CIB was worth another $5 in your paycheck. Of course, getting shot at was not a real good way to go for a pay increase!
Not sure of the time requirements in WWII but they were long enough to make you think that 'this was a bad idea' long before the time was over.
Currently, the EIB is open to all MOS's but is considered a mostly Infantry Badge. There are many days of testing and if you are not Infantry it is very hard to maintain all of the skills necessary. Even at that, there is not a high percentage of troops who receive the EIB.