6 hours is a bit of an awkward length of time to be gallivanting from EZE. As you'll have to make sure you get back in time to clear security/immigration and take into account any traffic hold ups I'm not so sure it's worth the hassle or expense to be honest.
It depends which lounge you have access to.......they aren't great but the only really horrible one I've been in was the Amex one. The United and Admirals Club ones are perfectly okay. I haven't been in the IB lounge so can't comment.
EZE isn't the worst airport in the world to be spending six hours in you can still find a quiet corner somewhere if you don't want to spend all your time in a lounge and people watching is always fun while having a coffee.