The 400 gr. Magnum XTP is a tough bullet, but will expand on large game. It is generally a good penetrator. I have used it on a couple of large bears, several hogs, bull elk, bison and South American water buffalo (Argentina), and am very satisfied with its performance on that larger game.
Velocities have ranged from a bit over 1200 fps to nearly 1400 fps, depending upon the gun ( I use 3). Expansion has ranged in one case up to about .75", but is generally a bit under .60". Many bullets were never recovered, so who knows what they did? I consider the 400 too tough to expand on deer, although I have not shot one with it.
I would recommend the 325 for whitetails. The one hog I shot with it showed greater expansion than I experienced with the 400's. I'm usually a .44 Mag. (mostly with 240 JHP's) kind of guy when it comes to using revolvers for deer, so I may never get much experience with .475's on them.
In any event, a .475 will obviously kill any deer alive, but like you, I believe in expanding bullets for whitetails for quicker kills.