Doing articleship in Big 4 does not affect your final performance in any manner if
1. You manage your time properly.
2. Be a smart worker to finish work faster.
3. Dont be over enthusiastic for people may exploit you.
4. last but not the least, plan your studies well before.
I did my articleship in Big 4. It is not true that you will be confined to one area only. It depends on the place where you are. But yes, you have to stretch your working hours a bit. But the exposure level will be good.
I know many Big 4 friends who have cleared final in one attempt with the stipulated leave period also.
At last, the ball is in your court my dear.
you will have to decide based on all the opinions given.
ALL THE BEST!!!