The only ones I've used long enough to really compare are the Pure Energy tanks.
Model 98 with electro and LP kits
It's tough, it's 4500 psi, it's fiber wrapped, it comes with accurate gauges (in comparison to some), the tank can unscrew from the regulator while under pressure (no other tank can, I hear), I don't get much shootdown even if I try to really lay on the trigger, it's an ajdustable reg with a big range (300 to 900 I think), the adjuster is tourney legal, but easy to adjust, the rail system makes mounting it very stable and adjustable. It comes with durable parts, and I hear the service is top notch. It comes in different colors.
An on/off would be really nice. If you have the pressure set high you will vent when screwing the bottle on or off. I have had a couple little leaks, nothing major and they always went away though. Mine didn't come with the rail adaptor (I got it used). The reg dings up and nicks really easily. It's pretty heavy and bulky, and less versatile than a screw-in tank. It could REALLY use one more output hole in the reg.
I would say that if you wanted a durable, top of the line tank with only one or two features missing, but other features no other tank has, go with the Armageddon.
the armeggeddon does have an on off valve, its the same as the adjuster, doesn't take long to reset it either, just put it up to 750 and your set, when you're done, turn it all the way down, take a few shots to bleed the gun, and the tank comes off with no problem. and it's not fair that you bought your's used and it didn't come with a rail, thats the person you bought it from's weakness, not the system.