Yeah, Iron & Wine live was ever so slightly disappointing. On balance I like them on record a lot more than I like Sigger Ross, and he executed the songs well, but jam band covers it. Long noodly interludes between songs that don't really seem to go anywhere. Having said that, hearing some of the older stuff jazzed up with a full band was worth it.
And Bon Iver were fucking awesome. So good. If they're still touring with Bon Iver and you've never seen them before, that would swing it for me. If it's just a straight up choice between the two though, see Sigur.