Best Travel Bag for India

Hi

I am travelling around India for just over a month with a friend, just the two of us . We will be travelling by train and car plus an internal flight. I dont want to carry a large back pack, though will use a small backpack for daily excursions. I usually use a pull along case rather than a soft bag (as when I travelled solo around New Zealland and Malaysia). We wont be using buses but will need to store our bags unders the seats/bunks when travelling overnight on the train. Any advice from fellow travellers who have travelled on the trains in India.

Thanks

Ooma