I love my RX450h, but I had the chance to try a NX 450h (plugin) while waiting for a fast service intervention, and I had positive and negative feelings comparing the two cars.
NX , expecially in EV mode, was faster and really quiet, the stiffer chassis improved driveability, and infotainment (compared to my 2016 RX) is now up to date; even fuel consumption is far better in hybrid mode, but if you plan to use gasoline and not to charge electric, NX Hybrid has more sense (even with a little worse 0-60 time). The suggestion is for a NON Fsport choice.
And now, the bad: even if in most of time (more than in RX) engine is off (and then silent), when it goes on the sound is of 4 cyl, very silenced but different from V6 in RX. The question is: what I would do if I had the need to change my RX? Probably I would buy a NX450h, not needing more space and considering new RX has a four banger too, but at the moment I don't need , so I may wait new models, and sparing money (not irrelevant topic).