i was at Teds (edward's hall) self catered for 2 years and it was the tits
evatt, IH and Teds are the best ones. Bara is more for couples and not first years because the rooms are self contained so you don't NEED to socialise. The rooms are nicer thre but more expendamundo and it's not as fun
the food is shit for catered, but the dining hall/living on catered is much more social (but you can get a doctors note and live in catered but not have to eat/pay for food, but then there is the issue of feeding yourself and iirc catered doesn't have kitchens like self catered does so it makes it hard to cook)
if you don't know people in newcastle/at uon i would suggest living on college because it makes making friends so much easier and then you just move off campus. there are some great places and share houses near the uni. I lived in one last year that was pretty nice but a bit boring because the suburb the uni is in is shit if you're not on campus
as for a comparison between the three, i'm not sure. Teds was a blast. there are regular themed college parties but every college has them. The rooms in self (slf-catered) are bigger than catered and they're pretty basic but it's enough.
it's not that difficult to get on college in first year, because the intake is approx 70% first years and 30% returners so if you decide to go back on then it's much harder so in your first year make sure you get involved if you think you want to stay on.
evatt is very much like teds
ih is 50% internationals and 50% locals, when i was there it was mostly american international students