I've used both caps and lithium. both are awesome without a doubt, if you are only burping than caps are going to be the way to go. Without a solid alternator and some idle output you can only hold so long before you do need to charged the caps. but the burp output is proven greater over batteries. me personally I'm running caps in my daily on stock alt on a M3b and before caps i could never go full tilt without protecting. Now with 2 banks i can go full tilt and it will still play, but the voltage drops fast still because the caps have no charge. so maybe 4-10 sec constant bass note full tilt. but previous to the caps i ran a buddies juicebox lithium for a show for fun and i had 2 M3b's strapped at 1 ohm (.5 each amp) and could demo for minutes full tilt chilling at 12.6-12.1, honestly didst see below 12v, and still with stock alt @1500rpm. So if you need long term reserve with less weight or terminals, then lithium is the way to go. Now if you can use both together, thats a recipe for disaster, best of both worlds.
Fidelity--Built To Last--Team Sound Asleep