If buying refurb gets you one up from what you were going to buy originally but new, get refurbed.
Otherwise, buy new.
Personally, I treat refurbs as second hand, IE not touching it a 100 foot long pole. I don't do second hand parts unless absolutely necessary (EG EoL products). However this is only a preference and not indictative of the reliability of factory refurbished goods.
For me, parts are split into two categories: parts that die somewhat regularly, and parts that don't.
In general, anything with moving parts I would consider likely to die, and won't purchase refurbed or second hand. Hard drives, optical drives, anything portable (the whole thing moves!) etc. Also, I put power supplies into the likely to die category simply because of their function.
In the unlikely to die category are CPUs, memory, mobos, GPUs, etc. Unless overclocked, these guys are generally pretty solid for their entire lifetime, and I've got no problem buying them second hand because if they work on day 1, they'll likely still work on day 1000.
I don't want somebody's RMA returned parts unless it's a huge price break and still has a full warranty.
I bought a refurb mobo from Newegg years ago and it ran fine, but it was only $24 so not much risk.
No way I'd ever consider refurb storage or monitors at all.