I think halls are generally more expensive than student houses, but not by a great deal. However I would recommend that every fresher apply to go in halls as its by far the best place to meet new people. In halls you don't just see your flatmates, you see people in the flats above, below, and beside you, compared to a house which lacks the social openness.
I was in Robbins in first year and loved it. It wasn't the nicest or most welcoming halls, but there were no problems, there was an en suite in every room (which was a godsend) and we even had a balcony which was great. It is also situated in the student village which is virtually on campus. I'd say that Robbins/Pilgrin/Radnor are all fairly similar in standard, and would all be good to live in. Francis Drake and Mary Newman are obviously a lot nicer in almost every way, but the price reflects that, and a lot of people can't afford it.
We spent a fair bit of time in St Thomas/Teresa in first year and I thought they were both nice halls as well, better than the student village halls, but 5 minutes further away. I'd have been very happy living there as well, although I don't know what the price range is like. I've never been in discovery heights or central point but I imagine they will be pretty similar as they're both unite as well, and they are both within easy walking distance again (Discovery heights is just across the road from campus).
Astor house is supposed to be amazing but I've never been inside, but it is a good 10/15 minute walk from campus, as is Alexandra works which I wouldn't advise living in.
At the end of the day it depends on your budget and need for convenience. If you can afford it,go for Mary Newman/Francis Drake. If you can't then apply for one of the student village halls if you want to be super close, or the St Thomas/Tereasa if you would something a little nicer and don't mind being slightly further away. Bare in mind that if you do a business course, then a lot of your lectures will be in the Cookworthy building which isn't actually on campus, its between the student village and St Thomas/Teresa.
I also don't think which halls you're in matters hugely at the end of the day, even though a lot of people worry while they're choosing. I think the experience is made by the relationships with your flatmates, and I was lucky to be in flat where all 6 of us got on really well and became really close friends, and lived together in second year.