as you know, a capacitor is just basicaly a storage pot, it will store power until needed, yes its for spikes like if you take of suddenly, it also aids in keeping the esc and batts from wrecking so it does help, i put 1 or 2 extra caps on all my speedo's, i have notoced a diffrence, the main one being easier on everything, better response for the throttle etc, once you know how to do it it's esay to do the next ones

one of my speedo's caps are rated at 50v, 400uF but i put 63v, 400uF onto it, stores more charge but more of smaller ones (50v, 300uF) can be better than one big cap

in the long run, that extra power needed will reduce wear and tear on the system