Ideal skate setups can absolutely make a session just like magic, with everything working, but a board that doesn't fit well can make things a struggle all round.
And that, IMHO, is the real "lesson" of Ben DeGros' six years(?) of documented madness: He could do
all his tricks on
any set-up he had. But on some set-ups,
things just felt better, and thus were a little more consistent/fun to do.
I can do all of my tricks on a <14.25 deck, and on a >14.62 deck. But they simply
just don't feel as good (as 14.38/14.5)...it's like wearing someone else's shoes, even if they are the same size as you. Yeah, you can walk, but shit don't feel right. If you're fighting your equipment, some thing is wrong. Your set-up should feel like a natural extension of your body...not like you are wearing shoes that are too tight, or too loose.
EDIT: Another good analogy to WB/deck size, is proper bicycle sizing. If you're an adult, and you ride a kid's bike, you're going to be cramped up. Yeah, you will have a real tight turning radius, and it will be agile for turning, but you will feel constricted. Put a kid on adult bike, and they will be all stretched out (hard time reaching handle bars and pedals), etc. Neither case will you be really stable, comfortable, or be able to optimize the bike's performance. Get a bike (or WB) that fits you well, and shit is
golden.