Hi all. I have studied the difference between these phones and actually used both. In a real world sense, the 910C (exynos) is quite a bit better than the 910G (snapdragon) I had.
First, the performance generally moving between apps etc is better on exynos. I think you can actually notice it. In particular opening the camera is noticeably faster. You can see a comparison on the video titled "samsung galaxy note 4 - Snapdragon 805 VS Exynos 5433"
Second, also in that same video if you look closely at the camera results the exynos version had much clearer detail (less noise reduction) on foliage. I didn't actually test that on the snapdragon phone I had, but on the exynos version I have now, the foliage looks good in photos, and I've seen other reviews where they complain about the smudging of detail with Snapdragon versions.
Third, the voice recognition is muuuuch better on the 910C for some reason. I don't think it is the microphone because both of them sounded fine sounded fine when I tried them out with voice recorder. However "OK Google" voice detection is much more sensitive and accurate on the exynos. I can say it from across the room and it works. On the snapdragon I had to shout it from a maximum of 2 meters away for it to recognise.
Fourth, the S pen drawing is much more responsive. There's no lag between your stroke and the line being drawn. This doesn't affect anything functionally, but it does feel better, like you are using a real pen.
Fifth, and probably most importantly, the rear speaker is much better on exynos. This was the only thing I hated about the snapdragon version. It had good volume but there was no bass and the highs were really clangy. On my exynos version the sound is actually better than my S3, not that that's saying much but it's totally acceptable for a phone speaker. At least I'm not constantly thinking about how horrible it sounds. This may be a difference between the devices unrelated to the model numbers, however I noticed in reviews on the net they were more favourable to the speaker on the exynos tested devices.
For the snapdragon I've read that the 3D performance is better and it may have slightly better battery life.
I was expecting the exynos to have slightly better headphone jack sound quality, in fact that's why I swapped phones, but I found no difference. Sadly the audio quality from the jack is a noticeable downgrade on the S3 but then I think the S3 was a star performer in that regard.