IShares and Vanguard are both companies that offer a bunch of different ETFs tracking all sorts of indexes (including the FTSE 100). From what I can see they are both distributing, so they will pay out whatever dividends they receive from their holdings. As for price/performance, they buy/sell just like any other stock, but I would think they roughly track the underlying value of their holdings. The difference in the price you see there would largely depend on how big the etf is and how many shares it is divided into.