We used to know someone who worked for the OU and he said that Rabbonim call the OU all the time and then will put their sticker on the product, based on what the OU says.
When we go up to shamayim after 120 years I don’t think the first question we will be asked is “did you only eat heimishe brands and products?”
Personally, I buy what is cheaper. So if the ungers tomato sauce is cheaper than the hunts tomato sauce, I’ll buy the ungers.