Persistent variables can indeed improve execution speed if you use them in a wise manner that utilizes their benefits, i.e. to cache data across separate function invocations, thereby saving the need to reload or recompute the data in each invocation. Of course, you need to ensure that caching the data is ok for your specific algorithm. After all, a fast but incorrect result will always be inferior to a slow but correct one. If you do not use caching, then persistent variables will have no useful performance impact.
In addition to caching, any other improvement to the performance of your Matlab code will naturally improve your model's overall performance.
