My reasoning is based on what really eats up the most power.
Especially on GB the biggest power drain seems to come from GB killing things that need to run continuously and them restarting over and over.
Compcache allows you to "virtually" create more memory space. I have to imagine this, as well as larger VM Heap, helps keep certain processes from being killed that immediately restart and get stuck in that cycle eating up the bat.
It may be the opposite on a froyo ROM.
walkin the walk while tappin the talk