Network engineer or security engineer job? and why?

If you decide it for the sake of getting a job, you won't really achieve anything. Do what you're good at or what you feel passionate about. Both of those two fields have a wide variety of available jobs and both of them are critical for any organisation that relies on IT for their business/services. Just go for what you're good at.

Just choose what you do better.

Go with what you see yourself good at.