A difference that large should show up in the resulting cubes though right? You wouldn't even need to figure out exactly how long they took to freeze or which tray froze first, just put a heated water tray and a cold water tray in together and compare them after waiting long enough for both to freeze. That'd give you an idea of how much more/less water you'd need to compensate.

Honestly, smaller ice cubes is probably your best bet if you need ice in hurry either way.