whats the difference between html2canvas and rasterizehtml.js

Question

Apparently there are solutions to capturing screenshot of a web page:

Snapabug works by using an applet

GrabzIt I guess this is done on the server side.

Webkit2png is a command line tool, so not really part of the browser code.

There are probably other solutions that use ActiveX.

But I am interested in a Javascript only solution. From what I understand, both html2canvas and rasterizeHTML.js allow to convert html (in a web page) to an image. So, in what way is the implementation of html2canvas vs rasterizehtml.js different ? From what I understand both of them seem to use Canvas to generate the result. So in what way are they different? Which one is better ?