You'll need to be more specific champ...
The FOX Float series is an AIR series shock/fork - VANILLA is the term they usually use for the coil over shock and the coil forks.
THe piggy back you refer to is the reservoir you'll find on many coil shocks (rear end) - and that's a different kettle of fish to the FLOAT air shock.
Having said that, FOX shox are usually great. i have FOX float forks and Fox float shock and i'm very happy with them - you would most likely want a fox vanilla rp3/5 for heavy duty freeride use.
others may have more opinions on the cost/benefits of other shock offerings in this area - eg: progressive and manitou.