Concentrator or cylinder? And what about a demand valve?

A common question. What is known: most home concentrators give up to 5 L/min, the strongest about 10 L/min, and doctors note this may not be enough. A cylinder with a regulator gives 15 L/min or more. Some patients praise demand valves, but there is no firm proof they beat a mask: a comparison in 57 patients found no difference between masks. What do you use and what have you noticed? Sources: https://practicalneurology.com/diseases-diagnoses/headache-pain/cluster-headache-acute-therapies/31521/ https://sage.cnpereading.com/doi/10.1177/0333102414529672