Sanaa Qur'anic manuscripts is a broad category that should not be mixed up. There are two separate categories of significant Sanaa manuscripts -- early Qur'ans and the "Sanaa I" palimpsest. The early Qur'ans are what Gerd Puin was talking about in his famous interview in the Atlantic (referring to variant spellings, unconventional verse orderings, etc.), which is how most people have heard of them. But they are not really that interesting tbh except in terms of establishing what the original Qur'anic orthography was and how it evolved (which is what Puin is interested in). You are not really talking about huge variations, you are talking about how different the base Uthmanic rasm is from the fully vocalized readings that Muslims imposed on it. That's a fascinating subject, but the end result is more a Luxenberg type situation (radically re-reading the same rasm), not significant variations in the rasm itself. IMO, it is correct to say that the manuscripts show that Muslim tradition has made a relatively good preservation of the base Qur'anic rasm of the Uthmanic text -- what they call into doubt is the tradition of vocalizing and interpreting that rasm.
But the FAR more important find, and a separate issue, is that one of the Sanaa manuscripts is actually a 'palimpsest,' meaning it is an Uthmanic Qur'an that was written OVER an earlier Qur'anic manuscript, sometimes called Sanaa I. In other words, an EARLIER Qur'an. This palimpsest is sensationally interesting because it is chock full of major variations from the Uthmanic rasm -- it is a non-Uthmanic Qur'an, the only one ever found. The first examples of such variations were published by Elisabeth Puin and then Alba Fedeli in the late 2000s.
The neotraditionalist scholars Sadeghi and Goudarzi have published (in 2012) a full transcription of what they maintain the lower text says in half of the available manuscripts (other half has not been published yet). They argue that it is a "Companion Codex," akin to the non-Uthmanic codices that the Muslim tradition records, although the Sanaa I palimpsest apparently has 25 times (!) the variants that Muslim tradition had recorded for such companion codices. Sadeghi and Goudarzi contended that this palimpsest was extremely early, based on carbon dating, but Francois Deroche has subsequently (and I think correctly) rejected their claims, and dated it towards the end of the 7th Century.
We do not yet have much scholarly commentary on the variations and their significance. In some places, it appears the Sanaa I lower text has preserved the more archaic Qur'an text, and that the Uthmanic Qur'an has made additions to the base text. In other places, it appears the Sanaa I lower text added additional material to the more archaic Qur'anic text. So IMO it appears to be an early divergent form of Qur'an following the initial major compilation. It is not itself 'more original' in the sense of being a direct ancestor of the modern Qur'an, but as a sibling Qur'anic text it is likely to shed a great deal of light on what the putative common ancestor of the Qur'anic manuscripts was like, as well as the climate in which it was produced (what kinds of changes were being made after that point, but before the standardized Qur'an project of Al Hajj and Abd al Malik).
Links to this awesomely fascinating subject (there aren't many neutral descriptions so I included Muslim and non-Muslim sources):
http://en.wikipedia.org/wiki/Sana%27a_manuscripthttp://www.answering-islam.org/authors/oskar/palimpsest.htmlhttp://www.islamic-awareness.org/Quran/Text/Mss/soth.htmlhttps://www.scribd.com/doc/110978941/Sanaa-1-and-the-Origins-of-the-Qur-AnThe short version of all this is that it appears that the so-called Uthmanic rasm was rather well-preserved as we now know it in the Cairo text, but the Uthmanic rasm itself was a heavily modified form of a proto-Qur'an, and many of those Uthmanic modifications were later scribal additions imposed on the text -- not original content. A good example is the extra 'and in the hereafter' that was included in Surah 9:74 -- the shorter Sanaa palimpsest version of 9:74 (which omits that phrase) is much more coherent, and the "and in the hereafter" phrase rather clearly looks like a later interpolation into the rasm that Muslims now know as 'the Qur'an.' The rasm was very fluid at the stage when these texts emerged, and there was evidently little control against adding material that modified or explained its meaning. So what you have in the standard version of 9:74 is a scribal addition that attempted to add that you ALSO will be punished in the afterlife (not just punished in this world, as the Sanaa palimpsest version has it). An awkward addition designed to emphasize hellfire, and to remove the reader's possible perception that punishment would be *only* in this life.
A sensationally interesting subject, and we have just begun to get academic reports on it.
Topic: Early Christianity and the Islamic Jesus