Keeping warrants secret can
also cause harm, by preventing oversight. Even if you take a "balance of harms" approach (which I don't agree with in general if it doesn't take deontological prohibitions and fundamental rights into account), in general I think the ability to have secret warrants with correspondingly minimal oversight is far more prone to abuse than any added benefit it might theoretically provide.
Among other things, secret warrants eliminate the ability of a party affected by a warrant to contest the legality or scope of the warrant. Secret warrants also prevent the public from having oversight of governmental overreach and abuse.
The US legal system is not and should not be designed to maximize the discovery and conviction of criminals at all costs. (Though observation of its net effects might suggest otherwise.) The US legal system is and should be designed to presume innocence, and to not presume that anyone targeted by law enforcement is a criminal. Your argument is focused solely on whether someone will change their behavior in response to knowledge of a warrant and whether that will prevent the conviction of a criminal. Having to obtain warrants at all also makes it harder to gather evidence; having to target specific individuals rather than a fishing dragnet of everyone makes it harder to gather evidence; many things make it harder to gather evidence, and that's a feature, not a bug. It's the reason why "if you have nothing to hide" arguments are invalid.
> I disagree, and so do the courts.
Disagreement is not an argument, and a statement of the current status quo is not an argument. If you want to argue "that's the current law" then my response is "I know, it's wrong and needs fixing", and we're done.
The status quo for several centuries were that secret warrants could not exist. This changed opportunistically in response to an event that made people fearful, even though there's zero evidence that these expansive and easily abused powers would have done anything to help stop that.