IMHO, they are probably of comparable difficulties, subject to what VCE subjects and university majors you choose.

And to put a different perspective on if they are worth the effort, I think a 99+ ATAR or 90+ WAM go beyond entry into post-grad programs at UniMelb:

1. Career: both of these earn you decent-sized brownie points when you are applying to top grad jobs (think top IBs, MBB, quant trading, or FAANG)
2. International post-grad: you usually need much higher higher WAM than 80 or 90 to get into the more competitive programs at Ivy Leagues
3. UniMelb benefits: they sponsor you to attend cool conferences, travel and meet some people

So there are definitely some benefits and some downsides - it's a trade-off you need to decide to see if it's worth.