I can't compare different halls or what private accommodation is like.
The Costume Store was brand new last year when I moved in so we were the first lot of students ever to live here. It's a bit more expensive than the other halls but the rooms are brilliant - clean, new, all with a nice en-suite bathroom. Very fast and stable internet connection included in the rent (would recommend using ethernet cable instead of wireless, more reliable).
The kitchens are very big, even considering you'd be sharing them with 4-7 people, and often you have them all to yourself.
The building is on a side road with a Tesco Metro, a pub, a petrol station, bus stops and best of all the North Acton tube station (zone 2), with Central Line trains leaving for central London every minute or so (15 mins to get to city centre).
If you're lucky you might get a room with a view of central London - really cool.
I like it here. :) Staying for my second year.