As expected, the primary difference between Spandex and Mfg AT screens is the Fabric.
Spandex (Milliskin) has a much smoother surface. There is absolutely no visible weave or holes from even 1' away. As such there is no chance that Morie can ever occure
If ever a AT Screen could be adjudged as being 4K ready, Spandex fits that bill.
Sound wise, in actual tests 2 Layers of Spandex equals or surpasses virtually all single layered AT Material, regardless of price.
Affordability and Ease of installation both are features Spandex alone excels in.
Some...if not most Mfg AT Screens might produce a brighter image because of the difference in Gain (0.8-0.9 Spandex vs 1.0-1.2 Mfg. AT)
The latter seemingly being the only advantage Mfg AT material possess.
Taking your largest desired Screen size into play, at 120" diagonal and placing the w1070 at a throw of 11'-4" (mid throw) while putting Gain at only .08*
, you still achieve a full 17 foot lambert of reflected brightness. *based on using the Light Silver Milliskin to improve on the w1070's low contrast
More aural / visual advantages....easier to work with....less cost...., your decision to make.
Spandex is the Holy Grail of DIY AT Screens.