Urgent please

You have decided your artcileship on medium size firm. then select the firm only. students were undergoning articles at big size form and later joining employment have seldom chance to apply those knowledge. 

Practising CA will surely get the advanatags of work exposure in a big sized firm

in big size firms all the high level works are done by permanent staffs or Chartered Accountants and the articles are given very useless works and many times articles are engaged in one type of work only throughout the articleship period for example stock audit or vouching etc..

when the name of firm is not known to outside world, will i be considered in campus interviews or job

you will not be considered in campus interview just because you have wroked in a Big firm but the level of knowledge and expertise you have achieved whether by doing articleship in a big frim or in a mid size firm.