i own a GA G2 so , no doubt carbon wrapped bottles are better all round - but most sites will only do 3k!but the biggest 3k steel tanks you can get that are comfortable at all to use are 0.8L, so a 4.5k 1.1L will hold more air than a steely, even at 3k psi.
not to mention the fact that they are lighter, more comfortable and give you the option of getting a 4k fill when they are available.