A smaller model in the same generation will never be the same as a bigger one, assuming this is a smaller model, and the same generation, as naming implies, it will not be comparable, it might be on the benchmarks, even on the benchmarks that matter, but the whole story should also give the drawbacks.
In Search Advertising, the amount you pay (under GSP Auction) is a function of your pCTR. And guess who determines your pCTR? The Search Engine itself! :-D