No requirement for the carbon fibre bottle
A standard 'steelie' which will realy be aluminium costs about £30, can take up to 3000psi which is the fill available at most sites, is probably marked for 5 years life before test (but in the uk is valid for 10 years for aluminiums), and will last forever if you went to the effort of getting it retested
A standard fibre cylinder costs about £150, can take up to 4500psi, can be used for 5 years between tests and has a maximum 15 year life (and is viable for testing due to its cost/replacement)
The standard fibre is bigger than a standard aluminium which means the weight saving of the lighter type is insignificant. Only when you have equivalent cylinders is the saving noticable such as a 48ci stubby fibre cylinder because it is the same capacity as a standard aluminium
To make weight savings with light cylinders then ultralight cylinders such as safer are truely light. But cost a bit more and have a 10 year maximum life
Money wise aluminium cylinders give the best vfm for air per £ even if you throw them away every 5 years
Fibres are best selected as the particular size / shape to ergonomicaly fit you
Unless you go to some shops or ask people to try theirs so that you can find the best balance for you then I recommend sticking to an aluminium cylinder first and putting £120 saved into other items or playing
