Congratulations on your offers! Essentially, both universities offer good engineering programs, meaning that in order to make an informed decision, you should consider the specific field that you wish to study as part of an engineering degree and whether either university is better than the other in that particular field. Another factor that could potentially play a role in your decision is location (i.e. which university is more convenient to you in terms of transport?)
I would be inclined to agree with
@Run hard@thehsc in that USyd would have the advantage over WSU in the case of the standard Bachelor of Engineering (Honours). With that being said, WSU offers two engineering degrees, the standard Bachelor of Engineering (Honours) as well as a
Bachelor of Engineering Advanced (Honours). If you happen to have applied for the latter degree and received an offer to study it, then the choice between WSU and USyd would become slightly more complex. This is because, in addition to involving advanced subjects and further research, this version of the degree sets higher academic standards, with a minimum standard of performance required to remain enrolled in the degree. Additionally, three majors that can be studied as part of this degree are delivered in collaboration with UNSW, which constitutes an opportunity to learn and gain knowledge from academics of two universities (that is, if you are interested in one of those three majors).
I hope this helps!