If i have to pay the amount via UPI then i will prefer PhonePe this is my prefered platform, But if i have to pay on the Paytm then i have the Paytm postpaid limits so i will pay the payment via Paytm postpaid. I think maximum users has Postpaid limits on the different platforms like Amazon, Paytm etc.
The only thing that I find as a reason to use phonePe is the ease, comfort and convenience in doing what you want from a payment app. You get multiple competitors but you need to select for the best UX