Reading various comments on this site, my only advice is talk to someone who knows what they are actually talking about.
For instance, I filled a Balloon pilot's US DOT certified cylinder (tested in UK 2 years ago) to 200 Bar this afternoon.
Some MH cylinders (with CGA540 threads) are rated to 200 bar, most to 137Bar or 2000psi to the old fashioned.
And I agree, the MH EDS systems are by far the most efficient and convenient sytems off the shelf.
Drager (and other) German steel cylinders are OK, and MH systems available to match the DIN477 thread, but they are awfully heavy.