Don't quote me on any of my answers but...
- RMIT you have to choose your specialisation beforehand. There's no general Bachelor of Engineering like Monash, and you instead enrol into a course that is already specialised (e.g Bachelors of Environmental Engineering). Given this, if you're not deadset into pursuing a particular specialisation by the end of the year, I would pick Monash for the flexibility.
- RMIT is generally considered the best uni for engineering. No idea why, but that's what I was told by actual industry professionals and teachers.
- If you don't know what specialisation to pick, maybe try asking yourself: what specialisation do I find boring and don't want to do? This hopefully should narrow down your list, which you can then make a better choice from. Don't worry though if you have no idea yet - you still have an entire year to think about it, and for your interests to change and develop.