I drove both back to back a few weeks ago when I was in the same boat looking at lightly used 18s vs new 19s. I went with the 19.
Although there wasn’t a ton of difference, I noticed less body roll around corners and a more planted suspension overall. I also tow occasionally and I’ve read that the 19 tows better as the back end tightens up a bit.
I drove an 18 the other day after putting some miles on my 19 and noticed a bigger difference than I had previously with the 19 rolling a lot less in turns and diving under braking less than the 18.
I also REALLY wanted the upgraded stop and go adaptable cruise as I sit in stop and go traffic quite a bit and love that the 19 works all the way down to a complete stop without disengaging. The new Terrain Control on the 19s was just icing on the cake for me.
Good luck in your decision!