From another thread on this same issue. An e-mail from an Estwing rep, in response to the question of what steel their tools are made of:
"Our tools are manufactured from 1055 carbon steel, special bar quality, and heat treated to ASME safety requirements, which is 45-60 Rockwell standard."
I haven't ever had any issues with how well they chop or cut; and one of the reasons I like the 26" handled one is because the handle is round farther up the shaft, enabling one to choke up on it if necessary. Got mine for $30 on sale at Home Depot a couple of years ago.
The one-piece steel tool is also full tang, all the way through the handle.
In any event, its primary advantage is obviously durability. Some have commented that the likelihood of wooden or polymer handles breaking during use is not that great; but breakage during use is not my biggest concern. I want to know if I'm on an extended trip, far from the nearest ACE hardware, that virtually anything could happen to my axe/hatchet, and I wouldn't be up a creek without heat or cooking ability.
This thing would survive a fall onto rocks that would shatter the wood and polymer handles of other tools. It would survive if rocks, trees, or logs fell on it; whereas the other materials might not. I've seen the wooden handles of hammers, hatchets, and axes all crack simply from improper or imperfect strikes... that is virtually impossible with an Estwing.
Bottom line, if I'm just using the tool in a casual manner or mild locale, where replacement is a simple feat, just about anything will do. But if I'm really out in the sticks for the long haul, where I'm not going to be doing any shopping any time soon and replacement or repair isn't an option, in an environment where the tool is absolutely vital, I want indestructible... and not just from me, but also from Mother Nature.
As is the case with most tools, I guess the best choice really depends on intended uses and needs.