So there's a bug which makes v-sync choppy, but it's temporary and will be fixed. It's already fixed on Chrome 45 on desktop as far as I can tell - it solidly hits within 0.1ms of v-sync every frame. Hopefully the fix will make its way down to Crosswalk soon. I don't know why people seem to think that this kind of thing will be permanent.
When users complain about performance and send us a .capx, about 80% of the time they are exceeding the hardware capabilities of the device. You probably have no idea of all the exotic sorts of tricks developers pull off to get weak mobile devices to perform well. Construct 2 makes it a lot easier to design games, but also easy to throw in tons of content that hit hardware limits.
If you're worried about the file size overhead, note that is temporary too: Android 5+ has an auto-updating Chromium based webview for default Cordova apps which supports things like WebGL and Web Audio too. So if you target Android 5+ with Cordova you get no filesize overhead and as good a result as Crosswalk. Android versions update pretty slowly, but it's already about ~12% and will increase to a majority over the next year or so. Newer Android versions also correlate to newer more powerful hardware, so if you have a particularly demanding game it might actually be suitable to target Android 5+.
Crosswalk is our wrapper for Android 4.x compatibility, and it really does provide by far the best results on those platforms.