What is the difference between them?
you can aquire your share in future PTS honoring developers. At 8/21/14 two new DACs take there snapshot. So if you want to take your share you have to invest before in PTS, or you can wait after and by in the exchanges. I expect BTER and BTC38 will also really fast include the two new Bitshares Chains. A good startingpoint is maybe the wiki
http://wiki.bitshares.org/index.php/Main_PageThis updated snapshot picture is a good illustration. PTS is like a mothercoin that you get new coins for holding.