They are both great degrees to have. Computer science will be more marketable but you can get a pretty good job with a math degree as well. As for the systems degree, its nice but systems degrees get outdated pretty quick since they are vocationally focused.
For example, degrees like Math, Computer Science, Economics, Statistics are quantitative and academic (focused on critical thinking and problem solving rather than any particular job) so the skills you gain from them last all your life. You learn how to think, solve problems and basically be a versatile person and you can apply that to any job. Systems degrees are more focused on how to apply technology (not to create it) and jobs, so while they might give you more career skills, they might get outdated pretty fast because systems education is focused on technology used in business, which changes all the time.
Basically, systems teaches you how to use a program whereas computer science teaches you how to WRITE a program. Computer science is much more creative and useful (but also more challenging.
You can major in either math or computer science, whichever you like but definitely take many programming classes. As for systems, try some classes but for a major math and computer science are definitely better degrees to have. In fact, any employer would prefer CS over systems.
Basically, do either a computer science degree or a math degree with a minor in computer science. Don't try to do everything though (degree in CS AND MATH). If you can handle it, great. But employers will prefer it if you have good grades in ONE degree rather than mediocre grades in two degrees.
Also, who knows you might change your mind later and might not major in either. Just remember this: choose a degree which teaches you to think and solve problems (thats why employers prefer degrees like math, engineering, finance, econ, business). They give you analytical skills which you can apply anywhere and have a good mix of quantitative skills.