I have used a number of different slow cooker brands over the years. Most were Crock-pot brand, but I've used others. I've never been able to tell the difference.

Sure there are tools where brand matters, but in the case of a slow cooker I'm putting the burden back on you: find me any brand that is actually inferior or better than the others. I don't think you can.

Non-slow-cooker things like a pressure cooker (ie instant-pot) with a slow cooker function are inferior to a real slower cooker, but they don't claim to be a slow cooker either.