Hello Norman,
Thanks for the great question. First of all you used all your terms correctly and saying that a church is a john MacArthur church I don’t think means that anyone is idolizing Dr. MacArthur, it is a helpful descriptive of the type of theology that is taught there. As for your question there are several answers that will apply and an individual will need to see what they and their family needs when it comes to deciding to stay or leave. Number one is that the most important part of the ministry of the church is the preaching/teaching of the gospel. Dispensational and Reformed churches still have a very close understanding of salvation and if the Dispensational church is Calvinistic then there is a lot of similarity. Also both types of churches can vary in how the truths in Scripture are taught. Some churches will do this very well and other churches will not do this very well. All this to say that if you are in a church that is not faithfully teaching the Gospel and is neglecting the teaching of the Word than it is probably time to leave for a better church. If the Word of God is not being taught very will this can and often does stunt spiritual growth and sanctification. Don’t confuse this with someone who is not applying what is taught to their lives. If someone is going to a good church and they are not growing in their faith it could be because they are not applying the lessons to their lives.
The second answer to your question has to do with the truth of the Word of God. This is not about if one group is saved and the other unsaved. Both sides believe in the Gospel. However; the way most categories are taught will greatly vary based on each sides systematic/Biblical understanding of Scripture. So on one hand Dispensationalism will teach that the Davidic Covenant will be fulfilled in the future millennial kingdom but Covenant Theology would say it has been fulfilled in Christ. Dispensationalism will teach the same thing about the Abrahamic Covenant. And Covenant Theology will teach that it was fulfilled in Christ. These differences in theology have a multitude of differences when it comes to other areas of theology. I have heard many people say that their church is Dispensational but they don’t really teach Dispensationalism. I think if we were to examine the teaching of the church we would find out that they are actually teaching Dispensationalism but they just aren’t using the key theological terms. The point here is that I would say that a person needs to be in a church that is teaching the Word of God in the most Biblically true way. If I moved to another state and was looking for a church I would look for a conservative reformed covenantal Presbyterian church first. But what if I moved to a place that only had a Reformed Baptist church, what if that was the most biblical church in the area? In that case I would go to that church. If however; there was a Dispensational, non-reformed church in the area and that was the best thing in 100 miles, then I would go to the Dispensational church, and I would submit to the elders and I would be faithful to the services and I would use my gifts as a faithful member of the body of Christ. If in a few year there was a conservative reformed church plant in the area I would more than likely end up leaving to help them. This isn’t because the people are better or that the gospel is different it would be because I want to be in the most biblical church available.
So my advice to those who become reformed and then think; “Oh know should I leave my church?” I would say this. You need to be at the place where the truth of the Word of God is taught most accurately. So that might mean that you need to stay in the church you are at because although they are Dispensational they are still the most biblical church in the area. One thing that has to be considered is your family. If you believe that moving from one church to another will harm your family then at least it must be done with caution and slowly. This also has to be done after a long time discussing these theological changes with the leadership of the church. (Pastor and elders). They need to be given the chance to care for your soul. If a person is wavering between the two systems they will need to wait to leave anyway since they need confidence in the Word before they make a change that is that huge.
Please feel free to follow up if I have not specifically answered your question.
Thanks