I’ve been planning to start rolling out a contest for a while but needed to educate myself. First, I just learned the difference. With contests the entrant must “do” something ie upload an image and the other FB endusers vote. With sweepstakes, all one must do is enter, most ask for an email address. I’ve been using Tabsite for a tab but there’ something wrong with the site and won;t let me add an engagement app without re subscribing. Support said it was a cookie issue but  I don;t think so. I also think Tabsite is trying to do too much and a contest app at $15 per month is suspect. I’m going with Woobox and I’m going to do a sweepstakes because it require less end-user interaction (no uploads - no voting).
My questions (for anyone who’s used Woobox) are how are winners determined and how do you communicate to them they’ve won?
Also from how I see it, you really need to fangate the contest/sweepstakes page and drive traffic via ads because my experience has been getting fans to click tabs in mass is like herding cats. This adds to the cost of the campaign so I want to make sure I’m on the right track if any one can confirm this. 
That said – here’s the results of my research – this is a (Woobox) contest: http://goo.gl/MxTgD this is a (Woobox) sweepstakes: http://goo.gl/jpqpk
We have about 12,000 fans so here’s the pricing of all the apps I looked at under $130/mo including Facebook EasyPromos - http://www.facebook.com/easypromos/app_115697541838284 - https://woobox.com/pricing - http://www.votigo.com/solutions/pricing-and-plans.php - http://www.shortstack.com/pricing/ - http://www.wildfireapp.com/plans/promotion_builder - http://www.antavo.com/en/pricing - http://www.appforma.com/pricing - 

@brando-hills – unfortunately Offerpop is outside our budget for the time being. 

@mitch-rezman Definitely fan gate your sweepstakes.
As far as picking winners.. Woobox stores all the entry data, you’ll have that available in the ‘Overview’ section of the app. You’ll also be able to export that into an excel spreadsheet too. In the past, we have emailed the winners.

Hope that answered your question, good luck!
Alexandra