I get asked to comment about cameras and equipment from time-to-time. These posts are always popular, but I'd rather not write them, because cameras are not important. However, if this helps someone, then it was worth my time.
The new Nikon D7100 DSLR, which has Nikon's new (and excellent) 24 megapixel APS-C sized sensor, is a great camera for a reasonable price. How does it compare to the Pentax K-30 and K-5 II?
These three DSLRs are all good cameras, and you won't go wrong with any of them. They each have excellent sensors, they're all weather sealed. You could do professional work with any of them. But which one is the best? Which one has the best value? Which one should you buy? These are questions that you are likely asking yourself.
In my opinion, the Nikon D7100 is the best of the three DSLRs, but just barely. The image quality from the D7100 will be slightly better than from the Pentax K-5 II and the K-5 II will be slightly better than from the Pentax K-30. But we're talking slight here, even from the D7100 to the K-30. The differences in image quality from one camera to the next are unnoticeable, except perhaps with a close side-by-side study (and who does that, really?).
The real advantage of the Nikon D7100 is with auto-focus (Nikon's is better, especially in low light) and memory card slots (two vs. one). However, the advantage of the Pentax K-30 is the price. The D7100 and the K-5 II will each run you about $1,200 with a kit lens, while the K-30 will cost about $900 with a kit lens.
You won't go wrong with the Nikon D7100, the Pentax K-5 II or the Pentax K-30. If you simply want the best of the three, go with the D7100. If you want the best value, go for the K-30. If neither of those two matter, go with the K-5 II. You'll be happy with your choice whatever that choice is.