Rode ND4 or ND5?
 

Just curious. What is the advantage of the ND4 over the ND5 other than being self-powered? The single stereo mic costs over $100 more than a pair of ND5's but they have the same specs. I would be using it in clubs to record live music along with video. I also have a pair of Shure KSM27s and a brand new Edirol R-44 to record with.

The NT-4 is essentially a pair of NT-5 capsules permanently mounted in an X/Y stereo configuration. The advanatage is ease of setup - no need to fiddle with a mount for two mics. The drawback is you're locked into the X/Y arrangement - there are other stereo micing techniques that might be more appropriate in some circumstances and not everything is always recorded in stereo so sometimes you might only need one capsule. For example with two NT-5's you could set them up in your choice of X/Y, ORTF, AB, etc, arrangements or use them along with additional mics to cover each instrument individually.