After a series of foot races with horses the following results were discovered:
the rope bridle is faster than foot with no buffs, but not faster than "Jboots", etc.
the silk bridles are faster than "Jboots", run 3, SoW and SoE.
The Chain bridles are significantly faster than the silk.
The SK and Pally AA horses are faster yet than the chain bridles!
We have yet to race with the ornate bridle dropped in SS, but when we get one, we will update the run speed for you! Hope this helps aid in your decision on which bridle to purchase. Happy horse shopping!