Miniature wise what is the size comparison between a centurion and a crisis battlesuit?
They are fairly similar in height, however several factors make it hard to give a single canonical answer. 

First off there are several versions of Crisis Suit (CS from here on)... If we ignore "specialty" CS such as Commander/Coldstar/etc there are still two different versions. Add to that the fact that CS come w/ a flying stand and are fairly dynamically poseable which can change the height fairly drastically.