I have performance problems too. I exported C2 project using crosswalk and got FPS around 60. Same project using C3 export got fps in the 50s and stuttered a lot.
Crosswalk is a wrapper. Wrappers usually enhance FPS, but at a cost of features, stability and the bloat of including the runtime in the final build size. You seem to have a good fps gap. My own tests are so close performance wise, I ditched crosswalk a good while ago.
Ultimately, mobile is a minefield for performance. Always has been. Try and test on some different devices to see what you get. Never, ever, test on one single device as take that as a final benchmark. Ive tested builds on older hardware and actually got better performance.