First, do it! 2 wheels are tons of fun. That being said, with the amount of customization, aftermarket options, tire swapping, and professional suspension tuning available you can make any bike fit nearly anything you want to do, within reason of course. I've got a WR450 and ride with quite a few KTM only guys, everyone has a preference and every bike has strong points.
Prepare for blanket statements, opinions, and generalizations:
-Japanese bikes are more reliable, routine maintenance and a valve job after the first few hundred miles and you are set for a long long time.
-Japanese bikes are cheaper new and used. Parts are easier to find but the internet can equalize most supply problems.
-KTMs have the sweetest brakes and finest clutch feel out there, this can mean a lot on a multi day difficult ride with long miles.
-Dirtbike maintenance is pretty easy and there aren't many specialized tools required until you start getting into suspension work. This can be a plus if the nearest shop isn't close.
Find a used one, there are tons of people out there that think they want a 2 wheeler then sell it a year or two later before they even wear the mold marks off the tires. Also, I may have missed it if you've already made your choice, but the bigger issue is 2 vs 4 stroke. I vote 4 stroke for general exploring and trail running but there isn't enough time in the day to discuss that rider preference. Don't forget to budget a few hundred bucks for boots and a helmet at the least.
Best of luck.