The DR capabilities are better on the NX30...
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...over the NX300. Both will give you that same color tonality and as you said, the EVF on the NX30 is a big plus. Although I must say that compared with many other EVF's out there today, the one on the NX30 is nothing to write home about (other than it pulls out so you can use it vertically. Now do keep in mind that when the NX30 was released, it didn't receive the best of reviews.
The NX30 has a very plasticky feel and is exceptionally light. The NX300 has a better quality feel to it, but that could be subjective. Anyway, I recently sold my NX300 (I have the NX500) because I also have the NX30 - so no need to have two 20 MP's models on hand. I'm keeping my NX30 because of the following:
1) Has a better (read "cleaner") high ISO capability above ISO 2000 (as compared to the NX300) - but I would not go over ISO 3200 with the NX30.
2) Has the same great color tonality of the likes of the NX3000 and NX5000.
3. The EVF which is articulating - comes in handy with scenarios involving macro photography and when you have to get down really low. Just pull up and out and the EVF lets you do that.
4. The touch EVF is very responsive to be sure.
I use mine specifically for scenic and landscape scenarios as I don't like Samsung colors for skin tones (where Fuji rules).
Now do keep in mind that the NX30 takes a different type of battery than the ones found in the NX300 and NX500. So bear that in mind when looking for extra batteries as they "may" be more difficult to find.
Now as to your question, "Would I purchase the NX30 all over again, if I could?" Since I shoot with a variety of mirrorless cameras (Fuji X system, various Micro 4/3 cameras, the Canon EOS M system, and of course the Samsung NX system), I'd have to say "No." And why is that? Because on the Fuji side of the house they have some wonderful deals on the 24 MP X-T2 and X-T20 cameras that have great EVF's, superb low noise high ISO results and class leading Dynamic Range capabilities. The NX300 and NX30 pale in comparison. Technology does moves on.
A few NX30 samples taken with the kit 16-50 F3.5-5.6 IS Power Zoom lens. All shot in RAW.





