Why bro ?? What happens if u use them ? I dont find much difference btw slice and one card
BNPL are categorized as personal loans(this itself is not a good thing because it shows you are in desperate need of money unlike auto/home loan). Also, BNPL have poor fraud insurance compared to regular credit card because in case of any issue you will be bounced back & forth between the BNPL company/the partner bank/the partner website support(someone here went though this recently when fraud happened on flipkart paylater).
Onecard is a proper credit card & the partner bank issuing it is responsible for all the support regarding fraud cases.