I really haven't paid much attention to the HP figures of bikes that I wasn't interested in, but this thread prompted me to take a look. In particular talking about the R1200GS and the Super Tenere. I have found that Motorcycle Consumer News can be trusted, mainly because they accept no advertising, so do not have to answer to anybody but their readers. While I may not always agree with their subjective opinions, I trust their measurements and specs.
So, in looking at the Super Tenere. They measured 91.3 at the rear wheel on the 2012 model and 99.5 on the 2014 model.
There have been several generations of R1200GS's tested, starting in 2004 when they measured 80.2. In 2008, they measured 94.0 and in 2010 and 2011, they got 94.99 on each. BMW took a big leap with the 2013 model when MCN measured 115.65.
While these figures are interesting and show that there may not be much difference in the 2 bikes, depending on the model year, as Brick stated, these peak HP numbers do not in themselves show the characteristics of where most of us ride out bikes, the low and midrange. I seldom ride WFO, and if I do it is only for a short time, preferring to enjoy midrange torque while riding my favorite twisties.
In this particular discussion, it would seem that if someone preferred the R1200GS, and HP is important to them, they should upgrade to the 2013 model or newer. OTOH, if whatever each of us rides pleases us and makes us smile, there is no need to justify that to anybody but yourself.