What Driver41 wrote is 100% correct. Im a student of CA too currently doing module D. CA is risky as compared to MBA, while doing MBA you have an assurity that you will pass at the end (no matter how bad your gpa is, but still you'll pass). CA, for some is very difficult, many of my friends could not pass even one paper after 4 attempts, as Driver41 said you need to have good observation, good analytical skills, strong memory, brave heart, courage to rectify your mistakes, adaptability means being flexible, consistency. courage to stand up for failures and commitment to pass CA.
Two weeks back our result was announced and 2 of my college students committed suicide as they were stuck in the first module for the past 2 years. Compared to MBA you hear no such news of getting stuck for this much time. As driver41 said some people do b.com while doing CA, one of my very close friend did the same while doing his Module C and passed b.com part one, but due to this distraction he failed his whole Mod c. So in my opinion if you start CA just concentrate on it and just forget all other courses.
Many students find CA very difficult, their daily routine is 7-8 hours of study daily but still they get failed.One the other hand some do not find it that much difficult and pass modules by studying only 1-1.5 months before papers.( I do the same thing and thankGod I pass). May be you find it easy too.
In Sindh you have Tabani (Im not sure if it is spelled this way), which is an excellent college for CA and many of its students top each year. As far as I have heard if you take admission there your passing chances increase by a lot.
But on the other hand IBA is best institution for MBA and you are lucky that you got selected. I've heard from friends its a little tough and they are very stict on attendance, other than that its the best institution you can get to do BBA/Mba.
About the job, many of my relatives including my father are Chartered Accountants and out of these 18-20 people only 1 person is continuing his profession as a CA, all others changed their fields because they give a good salary but the work they give is too much and very tiring. Compared to that, I've never heard an Mba say he changed his career because of overburden or something like that.
In the end choice is yours, do think before selecting your course. Cheers