The local options for uncompetitive districts? They are fungible, except maybe minor differences on some pet issues.

They don't have to care about actually representing anyone. They can skip town halls, ignore requests, etc. Primaries are a very weak form of influence.

If you want numbers, reps in competitive districts hold more town hall meetings. And they also hold more personal staff (limited back in 1975) in their home states. This is kinda a no-brainer. If you have to care about re-elections, you'll try to help your local consituents.