I say it's comparable, and heres my two cents on the differences between whitetails and mule deer.
I believe there is a huge discrepency in the behavior of eastern whitetails and western whitetails. There is also varied terrain that can become a behavior changer.
I hunt whitetails in mountain country, no riverbottoms or fields for miles in any direction and nobody uses treestands. The vegetation is thick but with clearcuts, shots can be out to 300 yards. Mule deer are not uncommon in these areas and I usually see a few does every year and a buck every couple years. The two species behave similarly.
I hunt mule deer in high mountain and sage brush country, where seeing deer is easy, finding a big buck and then getting close to it with very little cover is the challenge.
Whitetails stop to look back just as often as mule deer. Whereas in open mule deer country you can still see a deer that stops 80 yards away, in my whitetail areas, 80 yards puts them out of sight due to the brush but I know they stop and watch.
Last weekend I had a nice 130 inch 4x4 whitetail bust from cover 45 yards in front of me and then stop broadside at 80 yards, if I wasn't carrying a doe tag at the time he would dead.
Whitetails are not supernatural creatures that are magically more elusive than any other deer species, the challenge of whitetails is just different than the challenge of mule deer.
No matter which one I am hunting, my boots will be on the ground sneaking through the woods and glassy bare hillsides and clearcuts.