I have been a fan of Shure SM57s all my musical life (33 years). However, around two years ago, a soundman at church (who often does sound for my band) put me on to the Audix i-5; I worked with him one night and heard it for myself on snare. A few weeks later, I acquired a second hand example; now here's the surprise....
I bought my first Audix i-5 for use on snare and guitar cabinet, mainly as an alternative to my SM57s; but then one night, at a rehearsal, I set it up to sing through. My band does a fair bit of rock and I use my pharyngeal range almost exclusively. Using that system requires one to "compress" his voice, which I find pulls back the volume a little; but by using a "close-capsule" microphone (like the SM57) the singer can engage closer to the diaphragm; when I discovered this, I stopped using SM58s. When using the Audix as a vocal microphone, the "popping" problem, caused by proximity, can be avoided simply by high-passing the vocal somewhere in the 80 Hz region, maybe 100 Hz. Now, in this band, I use this microphone all of the time. I have occasionally switched to a '57 because the results are similar, but I find the Audix is more forgiving if I move off-axis.
So what about the comparison between the Audix and the Shure?
Many people have written about which they prefer and I think it's a pointless discussion. Both mics are great mics in the studio or for live. I think the Shure is the benchmark; and if we think of it that way, then the Audix has a gentle scoop when one A-Bs the two mics. Personally I like both mics and I wouldn't want to be without either type. After owning my first i-5 for a couple of months, I bought a brand-new one from Thomann, with some vouchers I needed to spend.
This weekend I recorded a vocalist and we did a text-book microphone shootout to find out which mic he should use for his lead vocal. We eventually plumped for a Rode condenser but the Audix wasn't far behind and it would have turned in a great result if it were the only mic available. That's quite amazing, since it's not considered a vocal mic for the studio by many people.
If you need an all-rounder, that's built to last a lifetime and you want an extra flavour on top of a '57, buy yourself an Audix i-5, you will not regret it; and rock vocalists might be in for an extra surprise. This would be a great starter mic for anyone into home recording because it will do everything.
Likely uses: guitar cab, bass cab and snare
Surprise uses: vocals, toms, acoustic guitar (close up)
I like: everything about this microphone
I do not like: there is nothing I do not like about it