What i have been reading about both products is that both First Class products are among the finest in the industry, so i dont think you will make a bad choice with either airlines.
LH offers an identical (thus more consistant) cabin in both the A380 and B748. AF offers a newer cabin in the B77W and the A380 is slightly dated.

That being said, the MQM's you'll receive for this trip on AF is a significant benefit and I would go for AF