Out of curiosity, when was the last time you departed or transited CDG? I have extensive experience with both CDG and FRA, and in the past few years transiting in CDG on an AF/Skyteam flight has significantly improved and personally rate CDG higher than FRA when flying with LH/Star Alliance.

As to OP's question. KL's current J seat on A330 is very bad, but if you can route your flight via JFK, then you will get the new KL J seat on flights to AMS and on two of the several daily AF flights. I find the new AF J seat far superior to the KL new J seat. If you can get lie flat seat with LH both ways, you have no loyalty preferences, and the price is not significantly higher, then taking LH seems almost obvious.

I took the AF flight on an A380 to IAD last year in J and as it was a daytime flight, the seat was decent (the so-called AF full sleep seat) and the soft-product excellent. Would take it anytime again.