Quite a few years ago, I was flying (as a passenger) UK to Copenhagen, (I think it was an A320, but might be wrong,) for the whole flight in which starboard wing had no winglet and the port one did. The aircraft behaved quite normally as far as I could see, but my colleague was more than little concerned, and asked the pilot about it. He was told that it was quite normal and certified, and the only effect was a small fuel consumption penalty.