I had a similar dilemma last year (not a bad problem to have mind you
)
I got into Sydney LLB (Grad) main round and was really happy about it. I had even enrolled.
The only reason I changed my prefs for the late round was because Sydney didn't offer part-time, whereas the (then) UNSW LLB (Grad) did.
I ended up getting a second round offer to UNSW and I decided to accept that one instead. It was a REALLY tough decision though, and the only reason I did was because I needed to study part-time last year.
I have been very impressed with the UNSW Law Faculty so far and am still very happy with my decision.
Good luck with deciding!