In the argument in Sludge Bomb vs Sludge Wave:
Despite being a Poison-type attack, Sludge Wave initially appears to be a good move with a high Base Power. However, when you look at the list of Pokemon who receive Sludge Wave, an overwhelming majority of them can not use Sludge Wave effectively. Nidoking and Nidoqueen are two exceptions. With STAB and Sheer Force, Sludge Wave reaches a massive Base Power of 185, enough to plow through any Pokemon that does not resist it. Sludge Wave is also useful in double and triple battles, as it can hit all enemy Pokemon with a slight damage reduction.
Sludge Wave can only be abused by the Nidos. Sludge Bomb, however, is learned by a plethora of Poison Types that have high Special Attack, such as Venusaur, Roserade, etc... So, on paper, yes, Sludge Wave is initially better, but in reality, the only thing holding Sludge Wave back is the limitations of the Pokes that can learn it.