The FTSE 100 daily spread betting market represents the one that is most correlated to the present FTSE 100 cash index level. If you hold a position on the FTSE 100 daily overnight you will be charged a financing fee to take into consideration margin costs plus any ex dividend days for FTSE stocks will be applied.
The FTSE 100 future on the other hand is similar to the futures contracts that trade on LIFFE. The financing cost and dividends are already factored in this market so no adjustments are needed if a position is held overnight.
Note: No market maker utilies the FTSE 100 ‘cash’ index price as a source for its quoting since it is slow and dependent on too many variables. All spread betting and CFD providers make use of the FTSE 100 futures contract (the near month) and quote prices from this. Since the futures move much more rapidly, prices quoted on spread betting providers’ platform may sometimes be quite apart from what you might see on an index ticker (which are normally delayed anyway). Lastly, keep in mind there is no such thing as the FTSE 100… you cannot buy into it directly… it is simply a mathematical calculation of all the 100 stocks that make it.