If you are serious about still photography, go for the trade.
If you expect to do a lot of action video stay with the Go Pro.
You can get a new NX20 for the cost of a Go Pro 3+ at Amazon.
Is this a good trade? I have a GoPro Hero 3+ Black Edition and someone is willing to trade a NX20 with a case, 2 lenses, and an extra battery for my GoPro straight across. The NX20 has less than 2000 shutter count.

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