I'd already been wondering how long I'd stick with Pentax since their market share is tiny. Which means things like lenses aren't always available in Pentax versions.
These days Canon and Nikon pretty much have the market cornered. Both are good and which is "better" is heavily debated. Canon probably has the lead in video, but I shoot very little video.
I wanted an APS-C sensor, for a smaller camera and for longer reach with lenses. (due to the crop factor.) That meant either the Nikon D7200 or the Canon 7D mk2. DSLR's seem to be focusing on full size sensors, while people willing to settle for smaller sensors are moving to mirrorless cameras. I like my little Sony but for certain types of photography, a DSLR is still the best choice. I decided to go with the 7200. One (minor) factor was that the 7200 takes two SD cards whereas the 7D takes one SD and one compact flash (which would be useless to me). Both are recent releases so the models won't be outdated too soon. (The Nikon D5500 is quite a bit smaller and has much the same sensor, but it doesn't have the same level of controls and displays.)
I'm not really looking forward to the switch. I have the Pentax in muscle memory and now I have to learn a whole new set of controls. Admittedly the functionality is mostly the same but the way you control it and the quirks are all different.
Any complex system has parts you don't like. And Nikon and the 7200 are no exception. One thing I found right away is that there's no easy way to reset the settings. This isn't unusual, my Sony RX100 is the same. Maybe it's just because I'm forgetful, but too many times I've altered settings for a particular shot and then unintentionally continued to use those settings, ruining a bunch of subsequent shots. I liked Pentax in this respect. It had a green button that would reset the basic exposure. And you could also define what settings should be kept or cleared when you powered off. I had mine set to clear almost all the settings when powered off. At first I thought I had found the Nikon equivalent - two buttons with green dots that you held down together. But you have no control over what it does and it clears way too much, including switching to JPEG mode! I find it hard to believe that JPEG should be the default. On a relatively high end camera like this surely most people are shooting RAW. On the other extreme, turning off the camera doesn't seem to reset anything. You can turn the camera off in the middle of a bracketing sequence and when you come back in a week it'll want to finish the bracketing. I guess that makes sense if you have to turn off the camera to change batteries or memory cards, but that'll be the exception. For me it'll be much more common that I'll end up shooting with the wrong settings. But I'll live with it, like I do with the Sony.
Another quirk is that for bracketing the 7200 requires you to either press the shutter multiple times or switch to continuous mode, whereas Pentax automatically allows continuous for bracketing.
One good feature of the 7200 is that you can still shoot RAW in full auto mode. On the Pentax full auto forces JPEG.
One theoretically big difference is that Pentax has image stabilization in the body, whereas Nikon (and Canon) have it in the lenses. To me it makes sense to have it once in the body instead of in every lens. But Pentax lenses weren't especially cheaper because of this, and as long as you have stabilized lenses there's not much difference.
As far as image quality goes I'm not expecting much difference from the K3. There's a minor increase in resolution - the 7200 is 24mp whereas the K3 was 20mp. Low light performance and auto-focus might be a little better. However, for the last six months I've been forced to use my older K5ii while my K3 has been away getting "serviced", so there will definitely be a bump in quality from what I've been using lately.
Of course, this means replacing lenses, flash, remotes, batteries, etc. On the positive side, I replaced the 18-250 with the Nikon 18-300, and will be replacing the Sigma 150-500 with the 150-600 (due out shortly), so I'll have a little more reach with both. (With the tradeoff of slightly larger size.) Hopefully I'll be able to sell the Pentax gear and recoup at least some of my costs.
I haven't taken many photos with the 7200 yet. As a true geek (of a certain sort) I've been studying the manual first :-) These two were taken in the backyard while experimenting.
I'm a little sad to be joining the mainstream. Never liked to be one of the crowd. The first thing I have to do is replace that gaudy Nikon neck-strap since I have no desire to be a walking advertisement!