IMO the reason for the different bits is for more precision. A horse in a
double bridle can be given more precise cues which is why upper level
dressage horses are ridden in a double bridle. Similarly a top spade bit
horse can be given a very precise and delicate cue with that device. The
gotcha is that is mut be int eh hands of an expert. A sensitive person
can makethe most severe bit seem light and easy to handle and an
insensitive one can make a hollowmouth eggbutt snaffle a torture
instrument.
I firmly believe that the snaffle is the only bit to start a horse in and
can be used for most horses for most activities most of the time. As they
become more educated a change to a more precise bit may be in order.
Oogie McGuire - oogiem@dsrtweyr.com
Weyr Associates - Multimedia and Web Authoring Services & Consulting
Desert Weyr - CMK Arabian horses & saddle mules for endurance and show
http://www.dsrtweyr.com/~desertweyr/