In reply to Choss:
I've used / use all 4. Started climbing indoors at URC (20 years ago), TCA regular, occasional visit to Red Point and been to Bloc 3 times since it opened.
Nowadays I only boulder indoors (prefer shorter intensive sessions and works my weaknesses.
TCA and Bloc are both excellent. TCA seems to have more powerful font & grit type problems, Bloc a little more suited to limestone perhaps.
Bloc is taller but TCA is steeper, grades at both walls are sandbagged a bit but as long as they are consistent who cares.
Staff at both walls are (with the odd exception) really friendly and helpful; for me TCA has been instrumental in changing the Bristol scene in to a much more friendly, fun and diverse group of people.
Personally I am going to split my time between TCA and Bloc, I'm not a big fan of working problems to death so this works for me.
We are lucky to have such great facilities in Bristol but need to be aware that five years ago there was only one wall. If we want all the walls to offer the continued great service we need to make sure we take advantage of them and visit them all every so often ensuring they are profitable.
Wouldn't it be great if they could work together to offer keen Bristol climbers a "super pass" that let you access them all for an annual fee. I would happily pay extra for this and it might ensure that we maintain such great facilities.