I've had the pleasure of riding an '07 R1200GSA extensively and a '15 R1200GSA a couple times. Then I bought the AT. The '07 and '15 are very different so it depends on which R1200GS you're considering. The '07 is more like the AT than the '15 is. I sit more "in" the '07, like I do on the AT. I sit more "on" the '15. Both are taller than the AT. The '07 has lots of low end torque with a much heavier flywheel effect. Easily maintains traction in loose terrain. Runs out of steam at about 100mph. Just like the AT. The '15 has tons of power on top. Very responsive motor. But no flywheel effect, there are times when it's really hard to gain traction, tire just spins, even when in 'gravel' mode. The throttle is just too sensitive to very tiny on/off transitions and rocks the bike back and forth. Not as bad as my FJR, but without cruise control this would get very annoying. Both BMW's ride heavier than the AT, because they are. Both BMWs have 19" front tires and I suppose, like the S10, that's one reason they can rail paved corners better than the AT with it's 21". But there's a reason the AT has a 21" front and it shows when off road (even off pavement). '07 and AT have narrower rear tires (180 vs 160/150 ??) so they turn more nimble than the '15. The AT is unphased by squared off rear tires. BMW's are tubeless. AT can be made tubeless. AT has fork issues, but the '15 does too (separating from triple clamp). At least BMW addresses this. BMW front fork shock replacement costs about as much as the AS conversion on the AT, so that's a wash. The '15 fork seals (at least on my buddie's) appear to be made of the same cheese they used on the AT so that's a wash too. Easier valve adjust on the BMW's but hexheads have a limited lifespan (about 100k) before the valves recess and can't be adjusted, then need to spend > $3000 on new heads or build up the seats again. '07 BMW needs extensive clutch maintenance every 50k or so. Not sure about the '15. EDIT TO ADD: 400+ mile range on the BMW's was AWESOME! Especially in BC/AK/YT. If I were to ride mostly street with an eye towards sport-touring, I'd pick the wasserboxer if I could figure out how to fix the throttle. No, actually, I'd look for an FJ09/MT09 at half the price and twice the reliability and sport, just throw some half-adventurey tires on it. Low weight nearly always trumps more power. But throw in hundreds of miles of off-pavement and the AT is better than either the '07, and FAR better than the '15 ... especially if the dirt/gravel is wet.