Size wise how different is the height of the tau crisis battle suit and the imperium centurions?
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.