To put into perspective, Northern European countries such as Sweden and Finland are some 7,000km's from the equator. Sydney to Melbourne a mere 800 odd km's. Just 800 km difference on a mostly flat baron land, with both cities metropolitan areas having a very similar height from sea level. Sure there's a couple of degrees difference, but that's about it. Not that much of a "difference in climate" really is it?
IMO, I don't think the climate has anything to do with the difference in NSW's and VIC's "reported" death numbers. The difference in death numbers is probably due to NSW Health deciding for themselves who should be included in the death numbers (with CV, from CV, by CV, probably CV, etc, etc). The NSW Health Minister has a God complex after all. HE is responsible and HE will decide who is and isn't a Covid death, thank you. Have a look at his behaviour from 2:30min to 7:30min
HERE. Wouldn't surprise me at all if this goose is keeping the number of deaths low to suit his agenda.