What receiver are you talking about? My Pioneer Elite (as many others I would suspect) have the sub-out port(s) on the back, and internally to the receiver, you can set the crossover to whatever you want, including full range. Not that you would want to. The standard seems to be 80Hz, but I guess you could play around with it, or if you think that the sub has a better crossover or something.
If the equipment is doing its job, then it shouldn't matter which part handles the crossover. I guess if I was the type of person that liked to mess around with the crossover on a regular basis, I would set it higher on the receiver, and then let the sub handle the crossover. That is because in order to change it on the receiver, I have to go through a couple of menu screens, but on the sub itself, I just turn an adjustment knob a little bit.
That is the only reason that I can think of, but I really don't mess with it once it is set. Others may have different opinions.
