the overall components are higher quality then most Japanese brands. some past models have had problems with the bearing behind the clutch, this is not all but some, it has been corrected in the last 2 years I believe. go to www.ktmtalk.com
look for 4stroke or dual sport columns, search bearings for more info.
One advantage you would have is plastic prices are far less the japanese brands. for the price of a rad/tank side scoop for a klr650 you can buy 2 side panels and a fender or 2.
You might consider the LC4 400, no longer made. I have one, great bike, you would think reliablity would be excellent since the engine was designed to be a 640. It has great power (ride one) it'll do 150KPH. not the wheelie machine that the 640 is (DAMN!) but it doesn't vibrate very much either so for your guests a real plus. Buy the comfort seat ($90euros or so), the stocker is like a block of cement, also it has a high seat height, will your clients be comfortable with a tall bike? you can find lower links at www.emigracing.com
I haven't used them but heard good of them on www.ktmtalk.com
one other advantage of using KTM is most customer would view them as top quality (they are) .
I have several bikes including an LC4 400, KLR650, DRS350, since I bought the LC4 the KLR and DRS are going to be sold, the LC4 is a blast.
Post where your tours are and your decision, Good luck!