Hello,
I have a Pearl White/Camel interior 2002 SC430 and a 2007 RX350, so maybe I can answer your question. I bought the SC and absolutely love it. Now, I will tell you that with runflats on a rough road, it rides like a truck - very different from the SUV. However, I'm considering changing to regular tires and I hear on this forum that it changes the ride significantly.
You can't beat the versatility of the convertible hard top, plus the car really moves on the highway. My son goes to college 8 hours from home and I've taken the SC on the drive down to see him every time. Absolutely a fun car to drive...
Bottom Line, the rides are very different - you have to figure out what you're looking for - fun/zippy/sporty & low or practical/cushy/SUV-high. I love them both!
Good luck!