Match the tiles - should be easy enough

I no longer play (regular) solitaire.  Mahjonng Titans -  imagine the young prince in ancient China taking strategy lessons - is one of the games that came preinstalled on my laptop.
The popular configuration is the Turtle, then I discovered new types of Mahjonng Solitaire, and some secrets of the game.

Can you guess which shapes are the easiest to play?  Why do you think so?
Try some games first and then deduce which shapes are easy and which are hard.  I'll be back in a few days.

This is the OCTOBER 2011 post.