Just my personal opinion but presented here for your consideration…
You’re running at really high power levels but you have an ESC pre-wired with 12AWG battery leads and XT60 connector***. This is a performance “bottleneck”, the wiring and connector are too small for the current levels you want to run at.
You don’t want to void the warranty and replace the wiring but you’re wondering if upgrading the connector to an XT90 and using 10AWG or even 8AWG everywhere else is really worth the trouble and expense. Since a bottleneck already exists, can’t we just stick to 12AWG and XT60’s everywhere?
Short answer = No. Not if we want to prevent even more bottlenecking and power loss.
You have to get somewhere as fast as possible. You grab your only available board, an old 25MPH beater. You take off for your destination at max throttle and start cruising. There’s no wind and you’re steady at 25MPH. Suddenly you hit a huge headwind and slow down a lot. You’d love to add some throttle and get back up to 25MPH but you can’t.
This is your bottleneck. Then the headwind disappears and you’re back up to 25 MPH.
Does this slowing down for a while in that headwind mean you can run at a slower speed for the entire ride and not affect how long it takes to get to your destination?
Definitely not. In fact, we would want to go even faster than 25MPH in order to compensate for the slowing down during the headwind so our total travel time isn’t affected.
It’s the same thing for our wiring and connector bottleneck example. Because of the bottleneck we want to try to compensate for it as much a possible, not wire up everything the same as our lower performance bottleneck.
For some small setups or those not wayyyy over the capabilities of the smaller wiring and connectors there might not be much of a performance or heating difference when using larger wires/connectors everywhere else. But for high power setups or longer wiring runs or where performance is the priority we should maximize performance every place we can. Don’t add to an existing bottleneck by creating even more.
Your dollar or size/space budget can affect your decision but for max performance and less heating and power loss we want to compensate for any bottlenecks as best we can.
***Example based on a question posed in a post here.