Keep the battery cooling fan clean and the EGR apparatus clean and they are just fine. Those seem to be the two most neglected areas and they are simple to deal with if remembered. All I knew about them is here.
The Elantra is cuter but the Sonata N line gets the nod. She couldn't really explain why. I think she liked the digital dash which was similar to the Mercedes. She didn't drive aggressively enough to get a feel for the 2.5L turbo but she like the idea that the power is available.
My wife choose her car for similar reasons, it was most similar to the one she had been driving for 10 years.
That the Sonata is our current frontrunner comes as a surprise. My wife does not love my Camry so I didn't expect her to pick such a similar 4 door sedan. I did catch her describing the digital dash with delight.
I put a spoiler on her old car. Cost was very reasonable. It came painted to match. Install was much harder than expected. She seems to like it.
Went to the KIA dealer, hated the entire experiance. The KIA K5 does not have the digital dash my wife likes in the Sonata. We will not be buying a KIA unless something drastic changes. If I understand the Sonata correctly you can not have both Wireless Android Auto and the 10.25 Nav Screen. One or the other.
Update After spending some time at the top of the list the Sonata has lost its crown because it is too bla in the exterior. My wife says she LOVES the Challenger. I don't love the Challenger, prefer the Mustang but it isn't for me. We got smart and rented a Camero via Turo. There are no Cameros around here due to the chip shortage. A week should be a long enough test drive...