... more volume is better for starting off for paddling and everything, but once you can paddle decently and know where to be to catch a wave does it really matter as much? I had to borrow a real short board for a day before I knew what I was doing, so I didn't catch any waves but it feel like it was surprisingly easy to paddle.
The majority of pros ride really low volumed board, because they're fit and proficient enough to not require much extra volume. So overall volume... that number in liters, beers, or cubic feet that everybody refers to these days... really does not matter that much to guys surfing at that level, relative to other design elements. Foil... or volume distribution... matters much more, and you don't get that from a single number.
A lot about paddleability has to do not only with volume, but rocker and template as well. Combined, even a lower volumed board can paddle better than a higher volumed board, if foil, rocker, and template are dialed in.