Airline from Chicago to Paris

The obvious answer is, of course, "none of the above".

On top of that, you've specified the only two options out of Chicago for non-stop to Paris
in April. American starts seasonal service in early May.

If it's just you, I would try to fly mid-week when you have a better chance of the seat next
to you being empty. Bring an inflatable pillow, dress comfortably, and make the best of it.

comfort in economy seating

Isn't that an oxymoron?

A seat that a 5ft 5 in. person finds comfortable, may be miserable for someone 6ft 2 in.

We typically fly Delta from Minneapolis. A few times we were stuck on a code share with AirFrance. IMHO, Delta is better and now I make sure my flights are not a code share with at least AirFrance. KLM is fine, but still I prefer Delta.

The decline in airline coverage means you are stuck. AF charges a bit more for the front of economy and is supposed to have more legroom on those seats. We flew Delta out of Chicago in the comfort economy last fall but they are not flying direct from Chicago now so we re stuck with AF. WE booked PE which is crazy expensive for what is offered. If doing economy I'd make sure I had the 'comfort economy' type seats in the front of the main cabin with more legroom and if flying with a partner book window and aisle and hope the middle seat is empty. We had an empty seat on our flight and it let us sprawl and made the miserable flight less miserable.

If the costs are the same, I would choose whichever has the the later departure, offering greater potential of uninterrupted sleep. I generally avoid AF with their draconian carry-on rules and virtually inedible coach food.

It appears Air France is not the way to go. I usually upgrade to extra leg room, so hopefully that helps.
Thanks for your input!

and terrible wine!