i've had both bikes and both i would say are completely different bikes...
Firstly i'll start with the ktm which i had first.
Good bits:
The engine is a stonking engine especially when de-exhausted, airbox mod and emission stuff moved, whellies allday long.
A great bike off road with some knobblies on.
Great sunday bike
Bad bits:
Finish was decent but sufferred rusty spokes and nipples

.
Fuel comsuption was diabolical with as low as 101 mile on a full tank, normally 150 was the best i had.
Tyres lasted a typical 2000-3000 miles.
seat was very uncomftable even with the gel seat.
Screen buffeting was horendous, possibly the worst ever on a bike.
You had to oil the chain.
front fork dive was horrendous on the toad while breaking (but you got used to it).
Gre
Bmw 1200 gs adv.
Good bits:
300 mile range and 50 mpg.
7000 tyre life on the rear.
comfatble as hell, did have slight screen buffeting but no where near as bas as the ktm.
Heated grips, fog lights etc.
Anti dive front end.
shaft drive.
Bad bits:
dealers thinking they have you over a barrel.
corrison on the front cover, forks, and rear wheel and hub.
People say the engine is dull (i found it great, and yer, it's no hayabusa).
comparison:
If i was going to buy again, which i am. the bmw would win.
The reason it would win is i do no offroad, love the 50mpg on a run, comftable, shaft drive, 7000 mile tyre life, 33 litre tank and it's big (i'm 6'4").
slightly better quality, ooh and the £11,000 KTM are now wanting for the adventure. Personally i think the ktm is worth £8500-£9000 tops in my opinion.
Yes some of the BMW stuff is expensive and they offer almost 0 discount but for my use it would be superb for me.