The two breeds mentioned by you are very different in all aspects. So first you need to look into that area and decide. As for buying a pup, one should buy only from a reputed breeder. Where exactly are you based. The are a lot of boxer breeders. Yorky breeders you will have to look around and i dont think there are any as such, so for that you may have to import one from a good kennel. It would be better to go in for a breed which is available in India, so that you know what you are buying.
Also read articles on buying a pup etc on this website.