Edited thread title to be more descriptive.
I'm not familiar with the Sequoia's ride quality, but I would start by searching for reviews from sites like Car & Driver, Consumer Reports, Motortrend etc. to see what they say about the Sequoia, then doing a similar search to see what they say about the 14-15 CX-9 and compare.
The 1st generation CX-9 has a couple of known potential problems. One of them being the transfer case on the AWD version, and the other being the water pump. If the transfer case fails, you lose AWD but still have FWD. The water pump issue is more of a design flaw - if the water pump leaks, it will leak right into the engine, which can cause a ton of damage. That means keeping an eye on the water pump so you can replace it at the first sign of trouble. Replacement itself is also an issue, as its more involved than a typical water pump replacement.
This is just what I've read though, I don't have first hand experience with the 1st gen, but I'm sure others will be able to provide more knowledge and insight.