Fut: Index vs. Cash

[PPMig@xxxxxxx]

I have been investigating trading futures indexes like the S&P 500,   Value
Line etc. 
Right now I only have data for the cash indexes.   My question is:  I have
tested systems that run well against the cash indexes,  but I am wondering if
this will be true when tested against the actual futures index?    Any
comments on the differences between how the cash and futures indexes behave?
I plan on checking this myself,   but I will have to get a new data service.

Also,   any comments on starting with the Minivalue Line index vs. the SnP?
Value Line seems to be less choppy and more trending in the 4 to 6 week time
horizon
that I plan on trading.

Thanks    Paul