Hi Yohooshi,

Lower working pressure means bigger rams to do the job you want to do with them. Bigger means heavier, even if the materials used can be build lighter in themselfs.

Advantage of 8 bar is that you can source commercial parts. Brands, Festo, SMC, Norgren, Metalworks or even "el cheapo chinese".

In the end , the gas in the bottle can be compared with electrons in a battery.
The more work you want to do in a certain time, the faster both will be discharged.