I've used both to mic my banjo and I think the Audix is warmer whereas the Shure sounds more accurate. Anyone used both of these mics with different results? More volume at the same gain with the Audix, though, for what it's worth.
The Youtube 57 vs. I-5 shootout HERE seems to demonstrate almost the opposite of what you noticed.
I don't have any direct I-5 experience and use a 57, although I'm not a big fan of the plastic surround on the 57. The big this is these are both dynamics and as such they work great in situations like micing a electric guitar cab, but they are sorely lacking to accurately reproduce anything with a lot of harmonic content. A condenser (small, mid, or large diaphragm) will trump a dynamic many times over, but don't work well in high volume live situations.
For live use I'd personally prefer the 57 based on the Youtube vid if I had to make a choice. The 57 obviously had a lot more bottom and fuller sound than the I-5 IMHO.
I rather like my I-5 because in most amplified venues ive played the vocals & bass are usually way over done , mostly vocals , (crazy loud) so a brighter signal from my Banjo is OK , I also think having a dedicated Banjo amp & speaker helps me to sound more like a banjo.I guess its just hard to be loud and acoustically accurate. LM