I tend to disagree with the "problematic engines" comment regarding KTM motos.
I'm not trying to answer for Paul or defend KTM, but as a very satisfied customer I will say...
Over the past 20+ years of KTM ownership of various models, I have not had a single engine issue requiring me to abandon a race or ride that was not induced by me due to negligence either before or during the event. I am a firm believer in preventive maintenance. I will never drive, ride or fly any man-made machine to verify MTBF. I haven't had to abandon a ride due to maintenance oversight on my part either.
I have had only 1 KTM warranty issue in all the years of ownership.
The 2 stroke MX bikes and Enduros do have a very frequent maintenance schedule but that is simply the nature of 2 stroke design. Even so, the schedule is based on hard core use. 4 strokes have a longer maintenance schedule interval.
Like Paul I use my KTM 500 EXC as a dual sport moto; not a hard chargin', all day long single track enduro. Nor do I use it for Hare Scrambles and such. So I feel (and have) gone much longer between oil changes than the KTM recommendation. YMMV exceeding the schedule.
Also, the KTM clutch is one of the most "bullet proof" clutch designs on any enduro bike. Yes, they wear out, but are much less prone to JRA (just riding along) failures.
I have been wrenching on my motorcycles since the late 60s. I rebuilt my first hot rod engine at 14 in '68 under the careful eye of my friend/mechanic/mentor. So yes, it helps to be mechanically inclined and not worried about splitting the engine case.
I have owned a WR250 and it is a great moto. But like any other man-made machine, it too will have parts fail and require preventive maintenance. There is simply no such thing as a "maintenance free" motorcycle. But, learning how to perform preventive maintenance will go a long way minimizing the potential for a failure on the trail, far from civilization.
Best of luck with your choice. Enjoy the ride!