I'm not sure yet if I'm going to Distant Worlds. I won't know until closer to the time (but I most likely won't be).
As far as the different ticket passes go, the main thing that you can really miss for being with each other is in going to the evening event or not. (The Ultima pass will also provide instances like the Event Tour, reserved seating, and VIP registration, all of which I'm sure is optional). But ultimately the evening event is the one you don't want to miss - great chance for a good oul' session.
The price differences between going to the evening event and not is $20 - $80 for Thundaga, $60 for Blizzara - with a 12% discount using the TLS code, then $70.40 for Thundaga and $52.80 for Blizzara (but there is a small site service fee of under $4 for Blizzara and under $5 for Thundaga).
Or, if you know for sure you are cosplaying, then use the 15% discount code to save more.