GW 6 44 will have 425 mAh battery, my GW4 44 has 361 mAh battery.
This is an 18% increase. But the screen is a bit bigger (which is bad for battery life) and the CPU is newer (which could be good for battery life).
On top of that:
new wearos version - assumed to be optimized, but more feature reach.
new watchface format which should be more battery efficient - not sure if relevant for stock faces at all, but for 3pp faces - should be good
Sum up everything and.. the same 1-2 days on a charge.
At least according to current leaks.