Zap nailed it. Go to the interview. Whether you spend the $300 in study prep is up to you. I find it hard to believe there is no free gouge floating around for the new version of the test.

I was in a similar boat as you are. I had a CJO from Delta and an interview invite from Southwest. I almost didn't go to Dallas because of the stress and hassle, but my wife talked me into it. It was smart call. I did minimal prep for the SWA interview and went in and actually enjoyed it. All it costs is a night (or two) at a Hotel and dry cleaning for your suit. Options are good.

Good luck with your decision!