The most effective AI writing app available is subjective and depends on individual needs and preferences. However, based on the information provided, Jasper AI seems to be the most highly regarded AI writing assistant overall. It is praised for its ability to create all types of content and has a strong focus on brand-focused copy. Additionally, Jasper AI has good templates and a longform assistant, making it a versatile tool for a range of writing tasks. Another notable AI writing tool is Rytr, which offers a good price point and is still a respectable option despite not having as many special tools or templates as Jasper AI. Ultimately, the best AI writing app will depend on the specific needs and requirements of the user.