@Auditor55 The consensus was, I thought, that Auro3D, then DSU and lastly Neural X, if you are using it to process stereo. That said, for stereo it is probably best not to use any. I have tried up mixing stereo and for this I would pick DSU, but sometimes it makes a complete mess. However I am purely referring to up mixing existing Dolby/Dts formats below Atmos/Dts:X.
The speakers have all been level matched and distance corrected manually after the YPAO setup. I can get close enough to the heights to tell they are working correctly. If I select Straight versus DSU/Neural X then this cuts off all the up mixing from these discs and does not use the height. I know how this sounds, it's been the setup for the last few years. If it made no difference I would just leave on Straight and save the electricity on the Marantz.
I don't think I have suggested previously that up mixing is comparable to actual Atmos/Dts:X mixes. If I have implied this, then I apologize and retract that.
I have said I don't think that purchasing older movies in previous audio formats suddenly released in "Atmos/Dts:X" is worth a purchase, for example Harry Potter. I haven't checked these up mixed, but they sound fine as Dts HDMA mixes.
I think the experience of pseudo Atmos/Dts:X 4K UHD releases and up mixing existing Dolby/Dts dvd/blurays is likely fairly similar. In the future some of the older (last couple of decades) films will get the proper treatment and this may result in possibly good approximations of an original Atmos/Dts:X mix. I noticed yesterday John Carpenter's Escape from New York, The Fog and They Live are all getting new 4K prints. Since most of these were from the 80s and 90s, whether the audio has also been redone I don't currently know. I do know at £30 a disc each it is not likely to replace my Dvds of these.
Last night as part of the film rotations, I am working my way through the entire collection, I watched the Phantom Menace. The print was the bluray release with Dts HDMA. I up mixed this with Neural X. The initial invasion of Nabu, the pod race and the final battle with light sabers, Gungans and spaceships seemed all nicely improved. Still doesn't make Anakin or Jar Jar Binks any more palatable.
I will probably watch the other two tonight.
These are just my own opinions and as always YMMV.
PS, Bluray Mockingjay Parts 1 and 2 are actual Atmos mixes. Hunger Games is True HD and my Catching Fire is for some reason only Dolby. I was comparing the Mockingjay with 4 heights over previously no height just 7.1 setup.