Perhaps in this instance we do need to get a little 'sciency', as I think it's too easy otherwise to draw general conclusions from limited, specific circumstances. I.e., one person might use a space blanket in their sleep system on a particular night and conclude that it kept them significantly warmer --- and maybe they're right. Another might conclude that it did more in terms of adding noise at night and getting them wet by not allowing water vapor to pass --- and maybe they're right too in their particular situation. My own experience at trying a space blanket a few times in colder weather with my hammock was more towards the latter, FWIW.

Using a neo-air, my inclination is towards Rick's thought about the radiant reflector built in. Perhaps it's not as good at heat reflection as a space blanket, but the incremental gain of the space blanket might not be worth the hassle of adding it? Given that it only addresses one of four ways of heat loss (Conduction Convection Evaporation Radiation) and the suckers tear so easily (not a great approach for use night-after-night-after-night), I'm just not a fan except for emergency use.

Bubble foil: I have no experience. Indeed, weight and bulk per measured R-value gain could help put this in perspective, with the caveat that listed r-value for a specific construction installation might not translate to r-value as measured as part of a sleep system. I'd also be curious about durability, given the "bubble" part of it --- is this likely to slowly degrade as various bubbles pop? All materials degrade with use; ccf degrades quite nicely, slowly.

I suspect that with a lot of experimenting backpackers out there, if bubble foil was a great option for sleep systems we would have heard of it in this context a lot more often. Here's one short BPL thread on the topic, fwiw.