Have used only RN3 so can’t say abt others.but I don’t find huge difference in RN3 nd RN4.They won’t announce Snapdragon version of RN4 yet as that may hamper their RN4 Mediatek version sales. Redmi phones are great in Hardware specs but camera seems to be not that great in either of the phones.I saw videos of Redmi Pro Camera but can’t say it is great.OK OK types.