If it's refurbished from Apple, The iPhone will come with a one-year warranty, the display, the casing and the battery will all be new. And yes, their replacement/refurbished iPhones are very good if you intend on purchasing from Apple.
Hey dogslobber, it's a great idea buying refurbished phone instead of new phone is always good idea.
I have the 6S Plus & am considering keeping it for another year. The phone works well & it will free up the limited budget to get a new 10.5 iPad Pro. I use my phone a lot but IPad gets used most often followed by RMBP & then the phone.