Personally, I'd get the DG phone. At least you know where it came from, and have some recourse if it doesn't work properly.
On Ebay, people sell broken/stolen/useless phones all day long. Once you buy it, you are stuck with it. Yes, Ebay has it's complaint system, but that doesn't get your money back (even if they tell you it does) because it is too easy to work around.
A Note 5 is how old now? Yes, it was a good phone, but it is also from the days of locked to a network/GSM or CDMA radio not both and how far will it update?
Not worth the risk to me. Your mileage may vary.