1st. this is a very independent question, because you can't have done one or the other before, and you're comparing it to some else experience doing one or the other. You are trying to compare first time experiences that are affected by the experience, between two people. If you drove stick, then can you say it was easier to learn, compared to the other person that drove automatic, but found riding a bike just as easy to learn (time wise)?
Personally, I can tell you riding a dirt bike in my youth, did not help me learn to drive a manual car. I understood the principal getting into the car, but the whole using your foot on the clutch and having non-sequential gearing made it difficult to start for me. Plus I was use to the slipping of the clutch on the bike, compared to the timing/matching on the car. . Now, I prefer manual cars over auto any day of the week, traffic or not.