I have tried several UPI apps over the past few months - Gpay, MobiKwik, Paytm, BHIM, Freecharge, PhonePe and CRED. My preferences along with views are as follows:
1) Gpay - Simple & Smooth.
2) Paytm - App is slow (I don't think of opening because of this), clumsy, but payments are quick. I mostly use it for Paytm Bank.
3) CRED - Strictly for its rewards (now rare), else no point
4) Mobikwik - Simple & Smooth, but less payment options
5) PhonePe - Clumsy. Kept in phone only to check received money from other PhonePe users
Rest no point.