As mentioned, I would suspect that the E1 is the same as the A&K, as E1 guns are generally rebranded JG and A&K guns that get a little more QA work.
The CA is way more solid, but you'd have to expect that from a quality manufacturer. That being said, the A&K is also a hell of a lot cheaper, so it's a "you get what you pay for" situation. After all, you're paying well over $1000 for the CA whereas the A&K is in the $750-ish area.
That being said, the A&K is a beast. It's all metal, pretty solid, and shoots great. Out of the box it shoots 400 fps at a respectable rof. The down side is that it takes mini batteries, which is a bit of a letdown. Plan on getting extra batteries or a lipo.
As for the hopup, the stock hopup setup is shitty and has little to no effect on the BB no matter how agressively you set it. This gives you a very short range. I installed a Guarder clear hopup sleeve, and made an improvised bucking from a piece of 14 guage speaker wire. The hopup works great now. It was used by a friend at Border Wars 2 last year and he said the range was sick. He was set up at the end of a path behind some cover, and was picking off people like mad. He said that he could see peoples' BBs hitting the ground 20 feet in front of him, but he could still tag them at that range.
So for the money, I would say that it's a worthy buy. Be careful to not throw it around or drop it and you should be ok.
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