Being careful when speaking about the Sahaabah (radhiyallahu anhum)

I feel that it is quite easy to commit kufr if not being careful. I was debating a brother about birth control. I say that the Muslims should have as many children as possible to enlarge and strengthen the ummah. He said that quality is better than quantity and having less kids means each kid gets better resources. He then gave an example that the Prophet (peace and blessings of Allah be upon him) and his companions were able to defeat larger enemies. Here came the main point: I argued that “it was not because that Umar or Abu Bakr were smarter than Abu Jahl and other kaffirs in raw intelligence, but because Allah (Subhanahu wa Ta’ala) favored the Muslims against their enemies”. Basically I was saying that the “Sahaba were not smarter than the kaffirs in raw intelligence” but they won because they had the favor of Allah (Subahanhu wa Ta’ala). Is it kufr to say that “Sahaba were not smarter than the kaffirs in raw intelligence”?