FastTemplate and PHPLIB's Template classes are almost equivalent in functionality, but they differ in the way they work internally.
You could start playing w/ FastTemplate PHPLIB's Template classes, and look into the other ones later.
I had not done a straight comparison, i.e. define a layout and then implement the code in each of the (now 6) classes, and then look at the timings and difficulties. This could be a good topic for an article.
Good luck.