Is a redback worse than a black widow?

Both spiders have potent venom. Their venom is comparable because they both cause similar symptoms. They're ranked among the most venomous spider species in the world, although bites from black widows and redbacks are rarely fatal.

Is the Australian redback a black widow?

The redback spider (Latrodectus hasselti), also known as the Australian black widow, is a species of highly venomous spider believed to originate in South Australia or adjacent Western Australian deserts, but now found throughout Australia, Southeast Asia and New Zealand, with colonies elsewhere outside Australia.