When I was young, I eated both, depending on the day I might of had white or wheath, and find that both have a pretty good taste. Of course, they are different, and depending what sandwich you are making, you choose one another.
Sliced ham-Wheat
Bologne-Wheat
Tuna-White
Chicken (fresh chicken not sliced)-White
Sliced Chicken-Wheat
....
Overall, I prefer white when it comes to fresh meat or fish, and wheat when it comes to stored sliced meat.
But if I really had too choose one, it would be wheat>white