As far as the 414 goes, it really depends largely on the model and year it came out. AKG is one of those companies that has a notorious habbit of changing everything they make every year, and frankly I've given up interest/desire in keeping up with all the models of the 414, although there are some on this board who know all about their history.
For the most part, though, my own experience tells me the 414 is a much more neutral mic. Especially when compared to the NT2, which has some noticeable and intentional high-end boost going on.
The NT2 was the original inexpensive U87 alternative. Because it got such a head start on the competition, it managed to find it's way in to a lot of mid-sized studios. Because they never really billed it as "sounding as good as a U87," nor did it ever make any lofty claims, people began to appreciate them as having their own sound, although, cosmetically, it was obvious who they were fashioning themselves after.
Anyhow, the NT2 I like to think of as a shiny, colored mic with lots of sheen. The potential is there for sibilance issues, but obviously it's a great, colorful mic. Shiny and colorful without being harsh. Can't quite describe it, but it's obviously held it's own through the years without having to significantly drop it's price. It's a classic in it's own right, as far as I'm concerned.
The C414 is also a classic -- neutral, honest, prefered by many great engineers for drum overheads and spot vocal chores -- but I'm just not sure which one.