the ion runs at 180psi (stock) using a fairly large firing can volume. result is long-ish recharge rate, so at high rates of fire, unless you are using ups and have a good idea of fine tuning, may suffer from varying degrees of drop-off.
the epiphany incorporates a variable volume can (ie: a can with 3 sizes of insert, for 4 different volumes) allowing a reduction in gas volume, requiring a higher operating pressure (250-280psi). This higher pressure gives a huge decrease in teh recharge time, thus firing at high speeds allows you to avoid drop-off. if set up well it can achieve 20+bps (blackheart/aftermarket board, mind) with virtually zero drop-off.
the consistency boost is awesome - and unless you have actually experienced it pretty unbelievable - i didn't at first, then put the internals in and was gobsmacked.
the epiphany also has a better trigger than the ion and comes with a freak barrel.
the eos looks like it is essentially going to be an improved epiphany, with the same internals, but with a clamping feedneck, rail mount and on/off, new milling, frame, Bolt-out-back design blahblahblah
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