All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
In principle, dealing with non-Muslims is permissible unless they are in a state of war against Muslims. Since in the state of war, non-Muslims may use Muslims’ wealth against Muslims themselves. The Prophet used to deal with Jews in Madeenah. As for the priority, if the same product is available with a Muslim, then dealing with him is desirable, since he believes in Allah and mentions His Name before any act. If a Muslim cheats or acts treacherously, he should be advised. If he leaves his bad practice and becomes steadfast, then dealing with him is better.
For more benefit on dealing with non-Muslims, please refer to Fataawa 395743, 333871, 341263, 384016 and 88293.
Allah knows best.