Just one other point Acire - many of us have or have had spirited horses (myself included) so can understand what it is like to ride,train and compete with one. My own background is eventing and I have always had OTTB's for it so believe me I can relate! It took time (some more than others) but my eventual bits were a thick eggbut snaffle for dressage and SJ and a slim full cheek snaffle for XC. Did I win the first time I took a horse out? Nope, it took a few goes to place but they always got better each time but it was well worth it in the long run having horses with simple snaffle mouths.
Personally I can't quite make the connection between 'spirited' and 'bit'. Sure they might jump around, pretend they are going to rear, crowhop, scoot off sideways etc but it isn't the bit that is going to change that behaviour, ever. Only time and training will. To an extent, a gag bit may help control these types of behaviour but it really is just a mask. The actual goal isn't to hide bad behaviour, it is to address it and change it. Of course you never want to lose the spirit of your horse, you just want to be able to channel it into a more productive use.
Another reason that you might want to consider using a snaffle if you are going to get into eventing: It is well worth being able to ride your horse in a snaffle in the dressage and SJ phases as many horses will be far more strong in the XC phase and sometimes a stronger bit is warranted as is a need for more instantaneous stopping/slowing power. Many people use a stronger bit in XC for this reason. If you already use a stronger bit for everyday use then there is little point to using one when it really counts as the horse has already learnt to disregard it.