Fair questions. I have not heard the exynos version. My disagreement was/is with your blanket statement that you "need v4a for it to sound decent" with a snapdragon note 4, since that has not been my experience. Would you mind sharing the model and carrier of the snapdragon unit that you compared to your exynos? In addition to differing hardware, different carriers use different kernels...
As indicated, my T-mobile variant, N910T, sounds much better to me than my former Verizon note 2, and there is at least one other T-mobile customer who has commented that the N910T sounds very good after T-mobile's initial software update. Any other N910T owners care to chime in?
Regarding my es10's, I haven't done any formal A/B tests with my odac and self built o2 (which I also upgraded with my first smd project, agdr's booster circuit, http://www.agdraudio.com/Page2.html and a dual lme49990, for, among other benefits, a much higher slew rate and thus much lower TIM). I enjoy my odac/o2 quite well as a bedside rig and, when relaxing at the end of the day, have usually been inclined to plug my note 2 or ipad4 in via usb otg for the improved sound quality (with both es10's and alphas). My surprise with the note 4, es10 combo is that I have not felt like it was worth the bother. I don't doubt my o2 wins on the measurements. I hope to find time to do some critical listening over the weekend to determine whether I ultimately enjoy the sonics more with or without the external dac and amp.