Which platform you should use is reliant on your future application concept and target audience. Each platform has its unique revenue generation strategy. Users spend more money on in-app purchases and premium apps. If direct monetization is the objective, iOS should be chosen. Android users are more numerous, but they are less likely to pay for app installation and prefer free apps.
The more downloads the app receives, the more expensive the advertising becomes. If the goal is to manage user attention, Android is the way to go. We strongly advise you to start with just one platform or create a cross-platform application. This will help to expedite the project's debut as well as identify its flaws and make any necessary improvements. You will save both money and time by doing so.