The phrase "a more effectual" is correct and usable in written English.
It can be used when comparing the effectiveness of different methods, strategies, or approaches.
Example: "To achieve better results, we need to find a more effectual way to engage our audience."
Alternatives: "a more effective" or "a more efficient".
Short of a more effectual coup, Corbyn and his enemies are stuck with each other – neither being about to leave Labour.
The Poor Law, which was designed to provide a "more effectual Relief of the Destitute Poor in Ireland" (O'Connor, 1995: 68), was based on the ideological perception that people had a natural passion for idleness, and that disincentives were needed to enable the poor to evade poverty (see de Tocqueville, 1835).
Caroline may call Cindy a "crazy Christian," but the redemption that she's pursuing may not be any more effectual than the prayers she allows the pastor to say for her in her office after a tense meeting with her boss.
Much of the frustration, the analysts say, stems from the lack of any more effectual ally to which Riyadh could turn, as former European colonial powers such as Britain and France have even less influence in the Middle East and Riyadh is unlikely to find much common purpose with Russia or China.
Modigliani's superb way with line, which establishes not only shapes but weighty volumes, can seem a surrogate for yet more effectual action with a chisel; and the sameness of faces, as he rendered them, is less disheartening in three dimensions than in two.
for making more effectual an Act in the 8th Year of the Reign of Queen Anne, entituled, An Act for the Encouragement of Learning, by..
In order to ascertain conservation landscape strategies more effectual, there is an immediate requirement for coordination between farmers and conservationists to improve livelihood of farmers.
As a result, β-cyclodextrin-curcumin complex was more effectual than free curcumin in telomerase expression inhibition.
Primary prevention that controls a common source of exposure to proven and probable carcinogens is far more effectual, and cost effective, than persuading thousands of persons to each change their individual behaviors (Asaria et al. 2007; Doyle et al. 2006).
While one method may be more effectual than the other, they are not the apples to oranges comparison you imply.
In the encyclopedic "Art of War," he suggests an improved design for forts, but he is still concerned with inner rebellion (he forbids an inner keep where the residents can hole up and tells us starvation is more effectual than siege).
