Okay, seriously--I have numerous 57's and a couple i5's.
Us old recording farts often get comfortable saying things like:
- it all depends on the source
- do what your ears tell you
- what color are your mic cables?
Okay, forget that third one, but we say things like that because it really is true. Especially in a case with two mics as similar as these. If someone were asking me about recording a heavy guitar and wanted to know if he should use a 57 or an NT5 (or any SDC), I could say with confidence--start with the 57 and go from there. But the 57 and the i5 are close enough that "follow your ears" and other vague Yoda-like statements (that would be "Your ears you must follow, young Jedi) actually hold true.
Now, having wasted all those keystrokes, I can say this. I remember being new to all of this. And sometimes you just want a real opinion. Even if it's lace with variables and doesn't match someone else's reality--it's at least a starting point based in experience.
So here's my experience: Knowing the reputation of the 57 and the i5 I played with them both extensively on amps and snares. I've also used them on bass, the bottoms of congas, brass--all sorts of things. But I found some niche mics that do all of those things better. So I'm back to amps and snare. In the end, I've got an i5 on my snare and 57's on three of my amps. Oh--I do have another i5 on an amp. It's a Vox (like that means anything in this context!) and in that case I found that the i5 worked a tiny smidge better than the 57.
But the real truth is this: If I had six 57's or six i5's instead of a mix of the two, I'd be just fine. And my recordings would sound just as good. Yeah, I'd likely EQ things a bit differently in the mix, but they're both workhorse mics that do a great job on the same types of sources.
Clear as mud?