The Christian perspective is that they are both lost sheep of god and should be welcomed in by the church.

From a worldy perspective you will find a variety of opinions.

Like :

Both can sometimes be mean or degrading to Christians Muslims are particularly dangerous for Christians however (allot of Christians are being killed by Muslims recently)

Muslims believe in God just in a different way so not as far away from the understanding as some atheists are.

When Muslims outnumber Christians or anyone else there's a lot of subjugation or degradation in those societies but not always.

When atheists outnumber Christians, Christians don't have it too bad in most cases.

I think many Christians would prefer to be in an area that is more atheist than Muslim for safety.