A factory overclocked card has been tested to handle the OC. So even with standard clocks such a card should be a little stronger in terms of longevity.
A slight factory overclocking doesn't give you a huge performance boost vs. a standard card. Rather than getting an "OC beast" of a lesser known brand, get something that has a known level of quality. The Gigabyte you linked to is a reputable manufacturer so you should get a silent and cool, yet competitive card. It's arguable whether the 6 GB model is worth the extra $50 against the 3 GB one, but for what I've read the smaller one has some other limitations, too. Personally, I'd like to get one but my current budget doesn't allow for it. People have got very good results with a GTX 1060 on older systems.
As for overclocking in general, my opinion is that it's good for prolonging the life span of older hardware at the point when breaking it won't be a big issue, used spare parts being very cheap. New gear should always be the best you can afford at stock clocks.
