Nice comparison clips to get the general flavors. I can really hear the 57's 180Hz bump, and of course, the mids. I dunno, the i5 has that spike right around 2k, maybe, that sounds pretty similar to a G12T-75's high end, if that makes sense. It's much smoother than that, but it still doesn't have that real organic quality that the 57 has. I honestly was reminded of a DI sound in a way. I suppose I'm just used to the 57 too much. Either way, I'd still take the i5 over the 609 from all the raw clips, mixes and live apps I've heard.
I'm intrigued with the above post on 57s for rhythm and i5 for leads. That's just genius -- brilliant, really.