Keep in mind the first two inner bands on a world cup booster are sewn together and don't provide the same elastic qualities that you get out of an expert booster. An expert booster has 3 equal elastic bands that provide a lot of performance qualities (especially on 3 piece boots like full tilts since a cabrio design uses the front of the boot for it's performance qualities, versus an overlap boot that use the spine on the rear of the boot) A lot of people just buy the world cup because they equate stiffness to purely skier ability, even if they only weigh 140 pounds. At 175 lbs myself I only use the expert booster. The world cup still has elasticity, but you can't really use it to its full advantage unless you really are a heavier person. The intermediate is usually one I sell to the groms still growing (or just very lightweight skiers) as it only has 2 elastic bands.
In short, don't get caught in a dick measuring contest if someone is telling you to just get the World Cup without factoring in everything.