this is a very interesting though and in reality it would be true, but we have definit and unchangeable circumstances that favor belts over trains in certain areas, so that they complement each other instead of replace

train has advantages in throughput and speed
belt has has advantages in ...

i do prefer belts over bots, as bots are just like a way to circumvent the biggest challange factorio has to offer getting stuff from a to b in the needed amounts
but sadly belts are very inadequad for some productionsteps, eg. one yellow assembler needs unmodified 2.5 green circuits per second to ...

0.16.5 has brought this issue up for me, BUT only on grasland heavy areas
zooming out more then about half way starts rteducing FPS
on open ground removing decoratives will stop the issue
and on desertmaps with low amunt of decoratives no problem at all

also trees affect the FPS hugely for me
if i ...

to diferentiate any amount of inputsources, in yur case accumulator charges of different powerlines you could use 1 decider per source
in your example just hook 1 decider up to the base and say A<20 output B as 1 and hook the second up to the defence grid saying A<2 output B as 1
then put all ...

i noticed something similar with my trainstations using splitter to balance the unloading of the chest
whenever the belt is not moving as fast as possible, the left (belt direction) part of the splitter is always drained fatser then the right
wzhat i do is merge 2 inserter outputs with a splitter ...