It kinda depends on what all is sandwiched between the slices of bread.
If I'm doing something simple like a BLT or PB&J, then multi-grain bread. If I'm doing a grilled cheese or a caned chicken mixed with mayo (and either bits of cheese or bits of dried cranberry), then wheat will suffice. However, if I'm using enough sauce, meat, and cheese, then I'll probably go with sourdough.
