Daily bets expire, as you'd expect, on a daily basis. Futures bets expire on 3rd Friday of the month you are betting on.
The spread on a daily is normally between 40% - 60% of what you would pay on a future so if you are looking to bet on price movement of more than a day or two then you must use a future, it's simple economics. If you use a daily it will close at the end of every day and you'll need to reopen it. Both daily's and futures should move more or less together no matter what the market does (obvioulsy we're talking about the same underlying market here like dow / ftse / s&p / dax / cac / nasdaq etc etc).
The futures price varies from the daily (also called the 'cash' price) not so much in movement but in value. This is because a futures price on any given product will factor in kown events between the present time (ie the cash price) and the date the future expires. The known events are normally things like dividend payments. An interest rate calculation is also added into the calculation. This interest slowly devalues over the life of the future until as we get almost to expiry there is now interest value left. So the value of the future is something along the lines of.......cash value + interest value - known events (divi's).
Hope this helps,
Steve.