I think the 45° join used in the States is safer. The reason being you join on the 45° for MIDFIELD downwind, so theoretically you should descend on the 45 to be at circuit height by the time you are downwind midfield. Anyone already in the circuit should be at pattern altitude by the time they turn downwind, and as the other aircraft will be joining at 45° it gives both pilots of both aircrafts better oportunity to see each other. As FFF says, if you're flying a powerful A/C and have a long runway, it is possibly to be near circuit height not far from the end of the runway. In the UK SOH Join factor into that the joining pilots inaccurate flying, maybe slightly low, maybe slightly further upwind than anticipated and you have a recepie for disaster. The 45 join can be combined with an overhead, fly over the airport 1000'+ above TPA, look at your windsocks or whatever, then depending which circuit is in use continue [or turn] outbound, and when at a safe distance turn onto the 45 and start descent to circuit height.
Cheers
EA
