imho don't buy the nt-1. if you have narrowed it to those two, for whatever reasons (suitability, availability and price probably), the spark is vastly superior to it in almost every way imho.
the spark isn't an LDC, it's a larger medium diaphram. it's also the same capsule as blue's top of the line handheld live vocal mic... which costs much more than the spark... and isn't nearly as sexy looking as the spark.
the cad m9 tube vocal mic is also really good and also better than the nt-1. I'd if need be rather even track vocals with a neutral mic like the cad m179 than use an nt-1 or an nt-1a. I can eq and otherwise process neutral mics to sound like good vocal mics - but I can't eq non-neutral mics to sound neutral in the mix. one more neutral mic is far more useful when you have a small budget. the nt-1 is not all that neutral - the spark is neutral enough to be useful for many other things while still being a little bit flattering to vocals. it's not an amazing vocal mic in the sense that some mics are just magical and the spark isn't all that magical but it is definitely a more pleasant sounding mic in the mid-range frequencies than the nt-1a I was using recently. I know some of the original nt-1s are slightly different sounding, but I personally wouldn't count on that.
if those are your only choices you'll probably be happier in the long run wiht the spark. imho. but I'm biased against that rode mic from personal bad experiences... some people have used them wtih great success.
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