Cannot comment on wifi use as i never employ it. I had and used the K-r for a number of years, then gave it away to friends upon obtaining a new K-S2 for a great bargain closeout price after the appearance of the K-70. It replaced the K-r as my secondary smaller, lightweight alternative when I need that aspect. So in both cases only for occasional use and backup. So far after more than 3 years, no problems with it at all, and hoping this will continue!
The advancements offered by the K-S2 over the K-r are numerous enough for the change. What I found important for me are- 1. better image quality; 2. even better low-light/higher ISO performance; 3. better construction also featuring WR; 4. articulating rear screen for shooting from various positions; 5. better live view; 6. better set of controls with 2-dial operation providing the full Pentax Hyper Program availability to allow instant on-the-fly adjustments to be made in "P" mode; 7. a much better VF- brighter pro-style glass pentaprism providing 100% view in the frame so what you see is what you will get instead of material appearing in your frame you thought you had omitted, a type of VF never seen on entry-level models in other brands; 8. all this in a body about the same small size or a bit less and at light weight as the K-r! A remarkable accomplishment and value.
Price should be quite low for a used one, even one with low use in perfect shape. Nice to have a 6 month warranty too!
---------- Post added 08-24-20 at 06:56 PM ----------
Originally posted by mashy
I also like the idea of the flippy screen as I need to take photos of myself and that would be very practical.
This feature works well too, and is very unique- the wifi button doubles as a secondary shutter release when the rear screen is in reversed position to point the camera towards yourself. You can even include a friend in the selfie by using a wide angle lens (with some perspective distortion of course due to being so close which might be correctable in post). Which lenses do you have?