Both are computer science courses but BCA-MCA for a specialized field in CSE while CSE for the overall coverage of the computer programs.
I hope you get the answer.
Good Luck  !!

Hello aspirant,

I haven't seen the BCA's syllabus but I have seen the MCA's syllabus & I'm about to be graduated from B.Tech in CSE.

Thus I can suggest you that if your main aim is to write code for the rest of your life then go for BCA & MCA.
Ofcourse my knowledge may be limited here.

If your aim is to deeply understand the workings of the computer & get accommodate anywhere where computers are employed then go for B.TECH. CSE guyz are very good coders but they're not just coders they're a complete package (knows many languages, knows electrical too, knows how to work in lowest level as well as highest level, tester, troubleshooter, management tasks, etc

Hope you understand 
Thank you