PNB has less exclusions. Pretty easy to qualify for fee waiver (use once every quarter). Online application process and higher application acceptance ratio. Low reward rate of 0.66%. For application to process it takes 2 months on average. App is decent. Limit provided might be low.
Union Bank has a few exclusions. Need Bank account to apply. Offline process. High chances of rejection of application especially if you hold multiple credit cards with high limits. Reward rate is 1%. App is decent. Limit is minimum 2L.