Slitherine

When you play as a Christian and take over a Muslim Region, should you disassemble the Muslim Piety buildings?
Thanks.

Having piety buildings exist in your regions from a different religion isn't bad. It's just inefficient, because they operate at no better than 50%. So it is best to eventually replace them, but it isn't a threat to leave them.

Thank you for the information.

Conversion will take longer if you leave the Muslim piety buildings in place. I have dismantled them in past games and found that conversion speed was much quicker and therefore less unrest and potential for revolts. Same applies to Muslims taking Christian lands.
It is a personal choice but I tend to demolish piety structures of an opposing faith.
Keep in mind some piety buildings are universal and are available to both religions so they don't tend to slow conversion like faith specific piety buildings do.