With the exception of an ebay bargain (£25 for a .79 with 18 months til first test, bottle cover and inline on/off - that was a nervous first fill, it turned out fine apart from a small leak - hence Bod's very good suggestion about only buying from people you know) I would always buy a 0.8 steely, I don't play at a competative level and haven't played somewhere that offers a 4.5k psi fill in years.
Carbon bottles do give you an edge, but certainly for my situation that edge is not worth the 400% price difference.
Carbon bottles do give you an edge, but certainly for my situation that edge is not worth the 400% price difference.