Nothing but great. New is new. Refurbished is not. End of story.
I’ve had my fair share of experiences with replacement devices that may of may not have been refurbished, but there was this one time O got a new iPhone with the same problem my last had, so I send it in right away, got a replacement with yet again the same problem, send it back in. Had 5 replacement until they didn’t offer mail ins from my location anymore… Granted, this was in 2017, but my definitely refurbished 11 Pro’s from last year gave me an unwelcome throwback.
Maybe it has nothing to do with refurbished devices, maybe Apples quality control just stinks by itself, no matter the device. All I can say is that I never, never, received a not-faulty device from Apple, reaching from $450-$2k. Don’t ask why I stick around.