ATG in Deloitte or Java/Spring in TCS ?

Hi dear Friends,

I am currently working in TCS India Indian top IT company and working as a java developer with Spring.

and now i got an offer from Deloitte and it is on ATG (not sure how the scope of ATG and how exactly it is).

but offer from Deloitte is good.

so now i am in confusion to take the decision of going to deloitte.

Can anybody explain me how is Deloitte in terms of growth and Onsite opportunities.

and also how is ATG and its scope in future ?

please give your suggestions friends..

Thanks in advance