I joined my training on jan 2008 after i cleared CPT and no one was there to guide me on training so i was unaware of big firms. I joined a normal firm. lately i came to know of big 4s.
It is better to join a mid sized firm becoz you can involve in many areas like audits of banks, companies, taxation, book keeping etc... You will gain overall ability to handle the clients properly.
In big 4s you will be assigned to a department like statutory, taxes and you will get to learn many things on that coz these biggies handle big corporate houses of india. But remember taking classes is little difficult in big4s as working schedule is vey tight there.
So, better join middle sized firms as in training the main thing you have to learn is independence and analytical skills and able to handle the clients..
Sharing my experince, i mostly spend my training in audits of banks and companies so i am quite confident on facing the corporates..
Thank you...