The Evening Pass only gets you into the Exhibit Hall, the pool party Friday night and the Banquet.
It does not allow you to participate in the tournaments, Live Quests, or panels.
The Day Pass allows you to participate in the Panels, tournaments, and Live Quests. You also get the t-shirt, goodie bag and in-game items.
Neither pass allows you to attend the Keynote on Saturday evening. You need to purchase the all access pass to attend the Keynote.
If you'd rather miss the Banquet which includes a TON of entertainement. Costume Contest, Giveaways, and more I recommend the Day Pass for $39.
I hope that helps.