It's a huge argument amongst some divers - is DIN really better than A-clamp?
Well, in terms of pressure, yes - A-clamp is only rated to 232 bar, whilst DIN is freely available in 300.
Does that make them better if you're using 232 bar? No, probably not.
Then there's the O-ring issue: On an A-clamp, the O-ring between the regulator and the cylinder lives on the cylinder. With a DIN fitting, the O-ring is on the regulator - a bonus when you're renting cylinders, as you know where the O-ring has been. It's also more firmly-held by the DIN fitting, making it less likely to come out.
The main reason, tho, for people pushing DIN over A-clamp is "It's a more secure fitting."
I always had trouble with this one. In all honesty, I still do. I've yet to hear any convincing reason for needing a regulator fitting that can withstand a hefty bang without coming loose. I've caught my cylinder valves on overheads in the past, and probably will in future. It's never been a problem, because I was going slowly enough that it was only a light blow.
The main reason I opted for DIN was simply that it was a more compact fitting. Having got used to it , I can honestly say I wouldn't want to go back to A-clamp. No amount of arguing ever convinced me DIN was the better fitting, but actually using it did. I'd recommend it to anybody.
More information is available from a UKRS page