Waaay too many opinions will rain down on you. Here's mine:
I am on my third TEX
First one: 2013 model TEX. Bought Jan 2013 0 miles, Traded in Sept 2015 at 41,100 miles - 0 (big zero) technical problems
Second one: 2014 model TEX-XC. Sept 2015 - Nov 2018. Traded in at 20K miles - 0 (big zero) technical problems
Third one: 2018 model XCx. Nov 2018. I am at 1500 miles
I ride off-road (true offroad)
I never wash the bikes
I leave the bikes sitting out under the rain, snow - there are tons of pictures of them sitting happily
I ride year round
I actually commute on the TEX in NYC. Yes, stop & go traffic, early morning commute, you name it. That bike is a work-horse!
... I have no complaints, no problems, no issues with my TEXs. I always said "I would buy another TEX in a heart-beat" I am a man of my word...
Super Tenere and TEX are not in the same class - I would put Tenere with Tiger 800 and the Tiger would still win.
I also ride / rode all the BMW models - wife has a BMW F700GS. When I rent I always rent GS (either 800 or 1200) so that I can beat the crap out of them and then compare them to the TEX. TEX wins every single time as far as I am concerned - and I never take other people's word for it.
You should test ride them both and buy the one that truly speaks to your heart. These are machines, and machines fail. What makes the difference is your connection to the machine...
.. is what I say :-)