Doing a bit of research/reading around the AVS forum came across this which talks about a lot of different screen. Granted we are probably WAYYYYYY over thinking this due to the cheap projector tossed in these machines. The projectors they guys are using to test these screens cost more then LE versions of stranger things haha.
DaLite HD Pro (0.9, 1.1, 1.3, 1.1 contrast): Low ALR materials with exceptional surface smoothness, and wide open viewing cones. The 1.1 and 1.3 look particularly nice at night. But only a bit better than a reference white surface (or paper) with combating ambient light. Really beautiful material though with a solid black backing. I'd go with this if I had a darker room.
DaLite Parallax 0.8: Interesting performer, but too dark, and not as much ALR performance as others, with my side-illuminating windows situation. Vertical viewing cone not as bad as expected (about like Slates, better than Black Diamond), but still would require me to mount the projector lower than I'm willing to.
Draper XH900X, MSX1000: good viewing cone, pretty good ALR performance, but both very grainy materials. And notably dark compared to SI's offerings.
SI Slate 0.9, 1.2: Amazing performers on axis, especially 1.2: bright, incredible contrast, smooth surface. Nothing even close. If you could just have this performance over the full viewing area... But the narrow viewing cone, especially horizontally, means at the side of the viewing area they go dark and lose contrast, even from the main viewing position. Add in our wide couch and they're non-starters. Even with lots of ambient light, the HD Pro beats out Slate at the image's edge. At night it's not even close. Definitely also the most prone to hot-spotting, which I define as "ability to discern the position of the projector by moving your head around". To be very fair, I'm really pushing these materials at a low throw ratio of 1.4, below the recommended 1.5. Throw ratio and viewing cone angle are physical inverses. I bet at 1.8 or 2.0 (and with narrow seating), they'd hold up much better at the edge.
SI BD 1.4: Not available in retractable so a no-go for me, but thought I'd mention for completeness. Very close performance wise, but I actually prefer the Slates (at the center of the screen). BD holds up a bit better horizontally, but a bit worse vertically than Slate.