ARPU spreads revenue across every active member, not just payers. It is useful for apps that earn from advertising or virtual goods as well as subscriptions, where non-paying members still create revenue.
For subscription-led dating apps, ARPPU and payer conversion usually tell you more. ARPU is roughly payer conversion multiplied by ARPPU, so a change in either moves it.
When comparing apps, check whether ARPU is quoted per month, per quarter or per year, and whether advertising revenue is included. Companies are not consistent, and a quarterly figure can look three times larger than a monthly one.