rdgreenwood wrote:
I'd take the 70-300 Nikon lens, say "Thank you," and leave. The 70-300 can be a "walkaround" lens; the 14mm, while fun for lots of things is a single purpose lens. If you love it, skip a couple of lunches and buy the 14mm without trading anything in.
You need to make up your mind, you say it is "fun for lots of things" and then say it is a "single purpose lens".
I have the same camera as the OP and am planning on buying the same Rokinon lens. I used to shoot with a Sigma 15-30 zoom on my F100 and shots with an ultra wide can offer a spectacular perspective on many different types of shots. It's not just a lens for architectural, landscape or astro photography although those are some uses.