— Physics is very CPU-intensive. You can get good physics performance out of Android, but you need a cutting edge device (Galaxy S3 and up) and keep object numbers very low (low as in: maximum 20 or so).
It's just how it is.. On high-end devices like the Nexus5 for example, the limiting factors decrease significantly. So over time the performance hit of wrapped HTML5 will diminish. Today, with devices like the Galaxy SII etc still around, you have to be extra careful, if you make apps based on wrapped HTML5.