I'm doing the Bachelor of Commerce Scholars Program and Bachelor of Economics, so I'll try to help you out with that one. I received a PM about the scholars program the other day, so I'll copy and paste some of what I wrote in my reply:
Honestly, the program doesn't offer a lot. It's relatively new (I think the first cohort started in 2011), so they're trying to improve it and add more things, but at the moment, everyone in the program who I've talked to seems to be pretty disappointed with the lack of extra things.
We sometimes have lunch/morning tea with faculty people, like the Dean and Course Directors and such. We also have access to some business skills workshops/seminars (though these are also available if you become a BusEco Ambassador in your second/third year).
We do get a scholars lounge, which is pretty cool and is my favourite part. There are couches (quite comfy to sleep in), cool chairs, computers, free printing, etc. but it's mostly just nice having somewhere private/quiet to go, especially if you need to study and the libraries are full, or around lunchtime when there are just people everywhere and you can't find anywhere nice to sit. It's also a good place to leave your textbooks/other heavy things you don't want to carry around for the whole day.
The $6000 per year scholarship is good, too, of course.
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Most commerce subjects have around three contact hours per week (usually two hours of lectures and a one-hour tutorial, though this varies with each subject). With a full-time load of four subjects, that's a total of ~12 contact hours per week. Most lectures are recorded and uploaded online, too, so there are many people who just skip lectures and only attend tutorials, meaning you could arrange your timetable so that you only need to be at uni two or three days a week.
As for how many hours of work to do outside uni, the uni recommends nine hours per subject, I think, but I doubt that anybody does that much. I've only just finished first year, so I'm sure I'm going to have to do a lot more next year, but I've managed this year with only doing a few hours each week for most of my subjects (and then cramming a lot in the SWOTVAC/exam period, as well as pulling all-nighters before an assignment is due or when a test is coming up).
I believe the hours would be the same/similar for Commerce at Melbourne.
I'm not sure about the exact hours in Law, but I assume it requires a lot more time and work (I hear there are four-hour lectures, and lots of readings);
sam.utute can probably help you out more here, since he's just finished his third year of Commerce/Law (and has also managed to be involved in so many extra-curriculars and things outside uni -- seriously, I'm in awe of him).
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You know, just before course preferences closed last year, a friend of mine came over and put the idea into my head that I should do Commerce/Law. But then I reminded myself that I didn't like law, and that I would loathe to be one of those people who felt the need to "use" their ATAR or choose a course for its prestige.
Definitely consider factors like travel time, the atmosphere at both unis, whether you need the scholarship money, whether doing law would destroy your soul, etc.
Good luck with your decision!