I've done this too some years ago, and I agreed with you then! However, since then, I have come across tracks that have a much more pronounced difference. To take it further, without even knowing it (Netflix rental, straight to play; no audio menu perhaps), I thought that hey this sounds lossy, I go to the receiver, and yep it was just DD. I do not expect to be able to do this with any consistency, and I do believe it's the rarity, but it HAS happened.
OTOH, a recent rental, Red, was with the lossy version and it wasn't all that bad. I think it just depends. Most movie stuff, I really don't think it matters all that much, as it might with music, except for the rare ambient scenes with sounds in a very resonant area. Hm, I'd describe it as spaciousness vs muddledness?
Parting shot, make sure to level match MCH vs SPDIF! You probably have Intellivolume, see if that can help make it easier.