Social life has already been covered here.
The lecturers from each university are people who do research in their field, and who actually do the stuff they're talking about, so they're cool. Each university has their fair share of crappy lecturers I assume, and each has their fair share of 100/100 lecturers, like UNSW's Mike Archer.
I understand that USyd has a more complex and crappy timetable selection system, whereas UNSW is done over the internet and it's quite easy.
UNSW's campus, despite it's suburban setting is much more urban in it's style. USyd has abundant lawns next to Victoria Park, whereas UNSW has concentrated nature areas and a lot of large buildings. I personally prefer USyd's campus, but only because of the area in which it's set around.
Getting to USyd is an ass pain. I know one person who gets off at Central and walks there along Broadway, and I know another who gets off at Redfern and has to walk there also. Either way, you've got to walk through a crummy neighbourhood which takes about 10-15 minutes depending on which side of the uni you've got to get to. UNSW has express buses from Central, which also take 15 minutes to get there during peak hour. It all depends on whether you're lazy, and if you like Redfern.
Also, if you live on the Airport/East Hills line, you're in for a sucky time getting there by train. Leaving early in the morning is fine, as there's always a bunch of trains that are City via Refern express trains, as well as a few via Wolli Creek trains. Unfortunately, if you're travelling in any time outside of peak hour, then the trains will go via Wolli Creek without fail, and you'll have to get off there to change to an Eastern Suburbs train to get to Redfern. That's why the person mentioned before gets off at Central, because it works out quicker. The same idea goes in the afternoons, although there generally seems to be a few more via Redfern trains in those hours.
Holidays are abundant at any uni, no problems there. I hope that helped a bit.