I guess we can either continue to disagree, or just move on.
But I will say that I don't understand how a 40 deck will be inferior to a 30 deck, but still, you believe what you believe, and I believe in mine.
You said it there yourself.
You can disagree all you want but that won't change the facts. This is not a matter of religion where you can use your belief as an argument. This is a matter of mathematics, and math says that smaller deck is better because there is less chance of bad luck with draw.
With 40 cards most matches end with you having 15+ cards left in your deck. Why take so many in the first place?
You should always take only as many cards as you absolutely need without decking out. If you deck out with 30 cards, there is probably something wrong with your deck, for example not enough damage or permanent removal.