I think the Rider test had them at the same weight.
I saw that on Page 38 Ray of the January 2012 issue, but that has to be a typographic error; it looks to me like they just copied it mistakenly (how can it be exactly the same!), also they tested the 2011 R1200GS Adventure with the 8.7 gallon tank.
As you know I worked for many years for Metro Mechanical, Inc. in Phoenix, I headed up the Pipefitting Division and my Buddy Dave Cooley headed up the Plumbing Division. When Dave got his new 2005 BMW R1200GS we put it on our certified scales at MMI and it weighed 515 lbs. and my 1996 BMW R1100GS weighed 540 lbs.
We were trying to figure out the weight difference between the two motos, since BMW was claiming that the new R12GS was 50 lbs. lighter than the older R11GS models. BMW Bavarian Bullshit: Only a 25 lb. difference between the two GS Beemer Boxers.
So, just looking at the three bikes' wet weight specs on their own web sites:
BMW R1200GSA 564 lbs
Yamaha Super Tenare - 575 lbs
Triumph Explorer 1200 - 570 lbs.
They are all within 11 lbs of each other.