I get asked often about equipment and what cameras I'd recommend. Sometimes it's one versus another. Those questions inspire posts like this one.
I'd rather not write posts about cameras, especially cameras that I don't own. I'd much rather write about vision, creativity, art, and the decisive moment. Those things matter, cameras don't. But posts about equipment are popular. It's what people want to know. So here I go....
On Tuesday I published a post on the new Nikon D610, and concluded with this: "The biggest news here is that soon the D600 will be available for less money. It is already one of the least expensive full-frame DSLRs available, but once the price is lowered it won't cost much more than a high-end DSLR with an APS-C sized sensor."
And that brought up this question: which should one buy, the Nikon D600 or the Pentax K-3? Both cameras have a 24 megapixel sensor, both have the features that one would expect from a quality DSLR. The biggest difference is that the D600 is full-frame while the K-3 has an APS-C sized-sensor.
In normal light, the image quality from both cameras will be similar. There really is not a noticeable difference between a full-frame 24 megapixel sensor and an APS-C 24 megapixel sensor at ISO 100. The D600 will have a slightly higher dynamic range, but not enough to be noticed. The K-3 will be slightly sharper since it doesn't have an anti-aliasing filter, but that sharpness will depend more on the lens of choice and technique than anything else. Speaking of lenses, there are many, many fine lenses available for each, so I don't think that should be a factor.
However, where the D600 will be the better camera is at high ISO. There will be a noticeable difference in image quality probably starting at ISO 1600. This isn't a big deal if you don't do a lot of high ISO photography, but it could be a big deal if you do.
The D600 has been plagued by problems. The shutter apparently likes to spit oil onto the sensor. Not good. But it is my understanding that this happens in only a very small percentage of the cameras and the odds are that yours won't. Besides, it comes with a warranty if you buy it new.
Once DxOMark tests the K-3, my guess is that it will be the highest rated APS-C camera on their site. If not, then it will certainly be #2. And that puts it only a few points behind the D600. Close enough that if you are considering one camera then you may be considering the other.
And now that Nikon has the D610, the D600 can be had for only a few hundred dollars more than the K-3.
So which should you buy? Neither choice is bad, and you won't regret whatever you choose. Go with your gut instinct. Personally, I'd choose the K-3, but only because I don't do a lot of high-ISO photography. The D600's biggest advantage would not be useful enough to me to make it worth the extra expense. Remember, though, that only you can know what's best for you.