My husband has COPD and is on oxygen 24/7. We have been using the cylinders for going out, at home we have an electric concentrator which is on all the time.
He is now on liquid oxygen for going out they have to be filled up each time you go out as the oxygen can evaporate. I do not have as much confidence in them as the original cylinders.
The liquid oxygen does seem to be lighter to take out perhaps we just need to get used to it.