Okay, red furniture might seem that it could be dated... But, as mentioned, the right shade, used the right way, I don't think would be dated.
I don't go for the sage furniture. Even though I do like the color a lot.
I just don't see that 'popping' or being warm and liveable. I don't know if one could do enough with any paint color or accents to make that pop and work.
When we picked out our unpholstery, I considered a really nice/beautiful sage fabric. The minute I brought home the large sample and laid it over my sofa... I knew it just wasn't gonna work. Not for me, anyhow. I do have some sage accents!
If you are going for the more casual 'Tuscan' look, red furniture might be the way to go. Again, I might shop around until I found the perfect shade.
If you decide that you do want a more modern updated look, go with the gray and get a cleaner more minimalistic modern look.
I think you really like red, and the Tuscan thing you have in your head. But, maybe because of the orange tone/cast of the red when you saw it, it just didn't pop.
Your taste might actually be changing and evolving into a more current thing if that gray really 'popped' and caught your eye.
Find a way to kind of compare a better red, and a gray that is being used in a better color scheme (not yellow).
I think it might be a good idea to take a fresh look at both decor schemes, together with the better color shades... and maybe then you will see right away which way you are really wanting to go.