I was the same had a choice between Pentax and Nikon both are excellent cameras and either one you choose will be an excellent camera and do the job for you.
I obviously went the Pentax I had a rough start with Pentax with a faulty camera and poor timing but that can happen with any camera. The only thing I find is the lens choice is not as great with Pentax and if you are buying for the WR capability there are only a few lens that fall into that category but choice is getting better with more being added and honestly there are covers you can get for them and your camera. If you decide Pentax I recommend the 18-135mm WR and 55-300 WR for a start these 2 lenses saw me across the other side of the world in Alaska through rain cold etc.
In all honesty in just under a year I rarely use either of these lenses I have upgraded to a k-3 and the sigma 24-60 F2.8 and the Sigma 50-500 but with time you will get to know your wants. The most important thing I don't think anyone has said yet is invest in a cleaning kit and a set of lens pens no matter which way you go. Change your lens in one wrong place and the specs will annoy you to no end if you are like me 😜
Also have to mention we have some of the kindest most generous people here I had a few angels that offered me a lend of a camera without barely knowing me when my k-50 died, the Pentax mob are mostly generous kind people. That is sometimes a good enough reason to choose a brand.
Best of luck in your choice all I can suggest is go play with both and choose whatever feels natural and comfortable to you.
---------- Post added 06-07-15 at 03:27 PM ----------
Originally posted by fcweissbach What if instead of the K-50 and 2 lenses (18-135 and a 50 or 30) I purchased the the K-3 used with a 18-135? Would the upgrade be worth it for the camera or should I still stay with the cheaper camera and an extra piece of glass?
---------- Post added 06-07-15 at 03:11 PM ----------
The cost of the used K3 with 18-135 would be the same as the K50 with the 18-135 and the 35mm prime.
Yes yes and yes the upgrade is definitely worth it my k-50 barely gets used anymore it's my back up