After reading loads of thread on BGG about "how to best use a single unit", I've decided to group some common strategies for easier reading (insted of scrolling up and down in some puzzled thread).
Here you will find Units detailed statistics wit some strategy guidelines.
Some BGG thread reference:
http://www.boardgamegeek.com/thread/170639
http://www.boardgamegeek.com/thread/347760
http://www.boardgamegeek.com/thread/105565
http://www.boardgamegeek.com/thread/394569