Same volume. I have to admit, I perform FBW a few times each year. Maybe 1 or 2 training cycles, only for variety. As I've always said, I am a proponent of the upper lower split because of the rest your are giving your muscle groups, and the ability to focus your energy, and your bloodflow.
I prefer devoting a maximum amount of blood flow to my muscles while I work out. While peripheral heart action typically burns more calories/fat, I'm looking for maximum muscular development. The best way to achieve that is to flood the traumatized muscle with nutrient rich blood. The more muscles traumatized during a workout, the more spread out the blood has to be. It should also be said though that I don't condone body part splits for anyone but true body builders.
The blood flow is one of the major motivators for me to opt into an upper/lower split.
Long story short, I want to devote as much energy and blood as I can when I lift, that's why I upper/lower split.