Personally, I prefer the racetrack circuit. However, that requires a lengthy shallow AoB turn onto downwind during which time a high wing aircraft is blind towards the active side of the circuit. In contrast, a 'square' circuit requires 2 short duration larger AoB turns between periods of straight flight. Hence the total 'blind time' is less. Low wing or high wing aircraft can cope with this together, hence it is, unfortunately, probably the better compromise for mixed civil light ac traffic.
Anybody flying beyond the normal visual circuit should be considered to have left that circuit; I suppose you could say "G-XX is visual with the traffic departing downwind and is turning left base" or something similar. Probably not in CAP413, but that assumes that people fly correctly! For example, the last time I went to Kidlington I was told to position behind the PA34 on final. Seeing one crossing the threshold I started to do so; however, I was told that I was turning inside the traffic. A quick reverse and I saw a dot on the horizon which was indeed a PA34 on hugely, enormously long final!! (Not my favourite aerodrome for many reasons - I was also very unimpressed to be waiting 'ready immediate' for departure only to be overtaken on the wrong side by some bizjet elbowing his way past the queue under some form of local priority system which does not appear in the AIP or Pooleys' and which no-one had briefed me about).
[This message has been edited by BEagle (edited 25 April 2001).]