When discussing the impact or outcome that is beneficial or advantageous, the term "useful effect" comes to mind. However, if you wish to diversify your vocabulary and express the same idea with different words, several alternatives exist. One option is "positive impact", which emphasizes the advantageous nature of the effect. Another phrase that can be employed is "beneficial consequence", highlighting the advantageous outcome resulting from a certain action or event. Additionally, "favorable result" conveys a similar meaning, emphasizing the positive outcome derived from a specific cause. These synonyms for "useful effect" can help add variety and nuance to your language, allowing for clearer and more engaging communication.