There are different types of refurbs, you can usually tell by how old the model is, and if the model is hard to pin down just use the CPU generation to determine when it was sold new.
The best refurbs are those that were returned shortly after initial purchase because the buyer did not like it, or made a mistake, or the unit has some minor problem that could easily be fixed. These usually sell for 50% to 70% of new price and, if purchased from the OEM outlet, come with the same warranty as a new unit.
The dicey refurbs are those that were used full time for 3+ years, usually lease returns. Sometimes they are fine, but sometimes they are rather beaten up and worn. These may only be worth the chance when you can get them for 20% or less of the new price. These generally come with short warranties, anywhere from 30 to 100 days.
All the refurbs out there with Haswell CPUs are lease returns. Ivy Bridge is even older, although I liked some Ivy Bridge laptops they are just to old to start with now. But refurbs with Kaby Lake, for example, are likely the first type.