then still, between those two mics, spark wins. more neutral midrange, faster transient response, more even overall makes it good for guitar (but I'm not certain about polar response - simply don't recall right now - but considering it's based upon a handheld vocal stage mic then it's potentially possible that it has a narrower pickup coverage than the nt-1. but the case/grill design often defines polar response and the spark definitely doesn't have a handheld stage mic's case/grille LoL so probably that's not really an issue.)
there are other alternatives, spark isn't the best mic out there or anything. but it's one of the good ones for the money. like the cad m179, m177, m9,
sennheiser mk4, and of course all of the old standbys (3035 etc). there are others obviously, akg perception series has a couple of useful models. There are a ton of affordable mics that claim to do what you want and many will work really well. But I think the spark is superior some of those mics I just mentioned for vocals and guitar use. And it's sexier. and it's from a renown microphone company.
I really would just buy it and you'll probably be happy and you can show everyone what a sexy mic you own. looks like it should cost $1000 and sounds good enough to get by as your main microphone. it'll sound good without eq or any magic, and as you learn what you wnat to hear it'll take eq pretty well. buy a better pop filter though since the little one it comes with isn't very good - cute, but not too good. and pop filters matter.