What history are you interested in? USYD has good modern history department and good ancient history but it's ancient history is all classics (Rome and Greece). If you want to study ancient Egypt etc Macquarie is the best.
Re uni's I don't think USYD and unsw dominate law in regards to employment as much as they used to. I now see quite a few Mac and Uts grads or paralegals at law firms. I mean theres still lots of usyd unsw students, but i do think uts and mac are catching up more than in the past. In the end, it's a difficult job market wherever you go - you just have to do your best. USYD may give you a slight edge, but if in the end your marks aren't that good, then it's going to be difficult no matter what.
The USYD JD is a great option, you will just want to make sure you get high marks to get a csp spot - full fee JD is very expensive. Regarding transfers, usually the recommendation is an atar of at least 97 and a distinction average, so the transfer may be a little difficult unless you do exceptionally wel in your first year subjects.
Re difference between difficulty of JD vs LLB - they are pretty much the same. JD may give you a bit more of a shock at first because Ta full law - but by JD 2nd/3rd year it's exactly these as LLB 4th/5th year. So not really much difference at all in the scheme of things.
Saying all that - I had a similar-ish decision to make many years ago (art/law Macquarie vs arts/law USYD and in e end chose USYD an loved it. My attraction to Mac was its amazing ancient history department but in the end decided USYD - it was closer to home
plus some other things).