I have a similar situation- we chose levers for the french doors. I just happened to like the look aesthetically I did not mind that they didnt match the round knobs

Have you done a search for "French Doors" on Houzz? Some great ideas come up and there is a variety of styles from levers to knobs to some very extensive hardware running the entire height of the door. The answer really lies in the overall style of your home. If you have a traditional home, maybe an ornate lever or glass cut knob works well. If you have a modern home look for a modern lever. The french door can have a different set of hardware than your other doors. Give it some personality. Good luck!

We had the same problem but ended up choosing the round knob on one side and a hidden opening on the other, we also paid extra for the blinds inside of the glass which was the best money we ever spent!!