When there is a difference in demographic indicator data that should not change between IHDS 1& IHDS 2, which one should I use?

For example, a respondent's age, sex, religion or caste.

Use IHDS 2 which has been more recently cleaned and updated.  We believe our second round of data benefits from our experience with the first, in terms of procedures and supervision, so IHDS 2 data is preferred.