I have had both, and I prefer the light. It absorbs less heat, is still fairly easy to keep looking clean, and, in leather, you can generally wipe things clean without stains, so the idea of the dark hiding stains is less of a factor. In cloth, dark has a bit more utility on that front.
Also, passengers have noticed and had positive reactions to the blue trim.

 

I do like the blue stitching that comes with the light gray leather, but I wasn't sure I wanted the rest of the dash to be light gray as well. Honestly, I would have bought my PHEV Niro regardless of interior color.

 

You better do what your wife says...If you know what's good for you LOL.

 

One thing we didn't consider in choosing the light grey for our Niro PHEV was reflections off the dash in overhead sunlight. It's pretty distracting, although polarized sunglasses do reduce it considerably. Not sure if Kia addressed this in the 2020 models by putting a dark color on the upper dash.

 

I get more glare from the glossy black around the shifter and screen than I do anywhere else. But I do wear polarized sunglasses, so I am going to have to take them off at some point and see if I have just been unaware.

 

When I first bought my 2019 PHEV Niro, in February 2019, I was much happier with the light color because the summers are hot enough that any dark color was what I was trying to avoid. However, I found almost immediately if you wear newer blue jeans even if they have been washed the color stained the light grey leather and cloth from perspiration. I was naturally disappointed, but I just got a inexpensive seat cover for the driver side only from Walmart that stopped that problem.

 

We got the lighter gray -- also paid for the treatment package to protect the leather. We've had it a bit over a year and a half and haven't noticed any discoloration or issues.

 

Was the treatment package that you got through Kia? If so how long did it take?