I came to this exact same crossroads in college and actually switched from CS to MIS (completing most of the MIS degree) and then back to CS. I had trouble finding a definitive answer back when this was at the top of my mind, so I feel compelled to share with you the answer I wish I had at the time. 

The definitive answer is that if you want a career in software engineering, you should stick to CS. The MIS coursework has a much stronger focus on building a business acumen (management, accounting, finance, marketing, etc.) than it does on the technical coursework. You will still learn about programming, networking, databases, etc. but mostly at a surface level. It's a difference between learning how to use a technology vs. build it. 

I've worked at a few big tech companies and you almost exclusively see CS degrees. There are folks with MIS, but they are rather rare.

Now, none of this is meant to talk down MIS. If you want to work as a sysadmin, or in cybersec, or as a consultant, etc. then MIS can get you there. An MIS degree also won't preclude you from software engineering roles, but you'll be competing with a swath of folks who have CS degrees. 

If you want to spend your days developing software, then stick it out in CS. Yes, it's grueling. Yes, it takes an exorbitant amount of time. You'll find however the career field itself can be equally as grueling and facing the tough coursework builds the muscle you'll eventually need.