Under the hood most (Chrome and Firefox) WebGL implementations use D3D9 on Windows through Angle (http://code.google.com/p/angleproject/ http://code.google.com/

Under the hood most (Chrome and Firefox) WebGL implementations use D3D9 on Windows through Angle (http://code.google.com/p/angleproject/ http://code.google.com/p/angleproject/) anyway. There is of course additional overhead in WebGL implementations, Javascript and using Angle as a translation layer, but this is a fair comparison, eventually those sprites are getting rendered by the same drivers and same D3D runtime.