>>725516986
I'd say speed/power sparks are preferred for Mile and Sprint at least, you can still hit 600 stamina pretty easily.

You can assign numerical values to white arrows knowing that the bursts are fixed and it takes 5 to trigger, so a white arrow is worth 3 speed/stamina/power by itself as long as you manage to trigger it, the value in practice will be higher since 2 arrows in the same training provide a flat bonus.

Since base training values are lower, a single rainbow can be less efficient than a really good training setup, like having 4 brand new trainees by themselves in stamina versus just Kitasan hanging in speed, it's more of a future investment at that point to proc a good burst later, focusing more on unity training is also a boon to the unity cup races themselves.

People suggest avoiding bursting on guts (for now) and wit is less efficient although I will pick it if it'll cycle a spirit burst readying a new one and if it has a good combination of my own supports or a wit rainbow.