An issue with your question is that "performance" depends on
1) What you are trying to accomplish, and
2) How well you program it in each language
In matrix/vector languages, a well-written program will outperform a badly written program. A well-written program will vectorize most operations. For example, you can compare the performance of various operations that use Level-1, Level-2, and Level-3 BLAS (basic linear algebra subroutines).
I have written many blog posts about how to write an efficient program in SAS/IML. Some of them are tagged with a "vectorization" keyword to indicate that the program includes a vectorized step that results in better performance compared to a naive implementation.
Full disclosure: I work at SAS and develop the SAS/IML language. In my opinion, these languages are comparable in terms of performance for many common data analysis tasks, so you might want to use other criteria to guide you.
- SAS/IML is integrated with the rest of SAS and shares syntax with the DATA step, so the workflow (DATA step, procedures, IML,...) for SAS programmers is straightforward. SAS/IML doesn't try to support every analysis natively. Instead, programmers call other procedures for statistical analysis and visualization and use IML for computing things that are not available elsewhere. Browse my blog (search: "proc iml" site:blogs.sas.com) for hundreds of examples.
- MATLAB has a huge fan-base among engineers, numerical analysts, and signal processing.
- R is best known for its packages, which provide a way to access statistical computations in every imaginable area of statistical research, visualization, and niche applications.
- SAS/IML is excellent at statistical simulation. I have written many blog posts (and a book) about how to simulate data in SAS.
- Support: Each language has communities that support its users. You might want to browse those communities to see which are friendly and focused. (SAS also provides free Technical Support for customers.)
One last comment: Since the mid 2000s, SAS has supported calling R from a SAS/IML program. Since then, other products in SAS also enable you to call R. In SAS Viya, you can use R to call actions (including the IML action). So the question does not need to be SAS or R. Your solutions can include both SAS and R.
Now I will bow out and let others express their opinions. Good luck!