This is tough. The last guy has the NT5's but has never heard the C-4's. I have the C-4's but have never used the NT5's. Frankly, I like the C-4's a lot, but only some of the time for overheads. For overheads, I use mostly Oktava MC012's and AKG C2000B's. The C-4's are more accurate than either of the above, which is precisely why I don't usually use them for overheads. If you like that sound on drums, then you will like them a lot. Good for jazz, country, classical percussion, or anything else where you don't want the sound colored. Generally, I like a little color in drum sounds.
I like the C-4's best for guitar, which I don't want colored at all. I love them on violin and recorder as well. For all of the above, I consider them better mics than the Oktavas or the C2000B. On the other hand, I can sing into a 2000B or even the Octava, but whatever the C-4's are, it isn't vocal mics. Sorry, I only know what I read about the NT-5's. Hope some of this is useful to you.-Richie