rfmax

I'm in the market for a '14 or '15 RX-450H. We've driven several, and find the seats bolster softer in the '14 models. Also, the ride seems to be smoother in the '14 models we've driven. Did Lexus make significant changes in these areas in 2015? Seems odd they would have with a new model coming so soon.

Clutchless

Probably not and even if they were, that is not a feature Lexus would advertise, such as an infotainment upgrade. It would be very expensive to change the seats or cushions. Failed seat cushions were covered in a recent thread and someone had a local car upholstery shop replace his with better stuff and also move the seat fan lower so thicker cushion could be installed.
I think you should just get a 14 if it is that important to you.

RickC5

Here's the thing about seats: If your rear end feels better in a '14 than a '15, then you should buy the '14. That's all there is to it.

Car seats fit everyone differently, and it takes a very long test drive to determine if a seat--in any car--fits you properly so you can enjoy long highway drives in comfort. I can't tell you how many threads have been generated on the Interweb regarding uncomfortable seats, but it must number in the thousands. It seems that lots of folks take a very short test drive--like around the block--then buy the car and discover that the seats are uncomfortable on a long trip. My test drive loop is over 30 miles long, encompassing city, freeway and curvy rural roads. It takes about an hour to drive it, and I can tell after my test drive whether the seats will work for me or not.

BTW- I find Lexus seats to be the most comfortable for me.