The thing is: they are MUCH more efficient than the software EQ that FiiO implemented that does nothing.
I keep saying: this is the best FiiO player ever.
Og x3 is indeed a very good player. i loved it for about 2 years. but then I had the chance to buy the 2nd gen for ~ £100. (Special offer.)
And I did not want to keep more than one player, so one of them had to go.
After 2-3 days of A-B listening X3ii came out as a winner. X3 classic has a more "inverse" u shaped sound (higher and lower end tends to die out compared to X3ii), while the 2nd gen is much more linear. Og is much darker, less refined, bassier, more powerful. 2nd gen is brighter, more balanced, much more detailed and refined, more linear, more balanced sound. Overall crispier, cleaner.
Og is more "old-school" hi-fi experience imho. It is a very good player, and will have its fans for many more years.
But the 2nd gen is a big step up. In almost every way.
Not to forget, pairing is an important factor when you judge overall sq. Og X3 likes more analytical and brighter headphones. X3ii likes a darker, 'bassier' kind of headphone.