Yep, not trying to offend anyone, but that more power (in HP and Nm numbers) understaning is technically uneducated (read: stupid) men's problem, that doesn't exist in reality. There are serious technical reasons why is it so.
Unlike other boxer BM bikes the GS is also trail-offroad oriented where you have not much to do with peak power like RT, S etc now have. On trail, loosed surface roads the flatness of torque curve comes in play, and especially the low-to-mid rpm (2000-5000) part power, not the high rpm part where the piston strokes are too dense and doesn't have
traction effect (read: basically wheel starts to slip on loose surface) put into back wheel through gearbox and final drive. It's also called "big bang" theory in motorsports - how piston timing and engine's concept how the piston angles transmit the energy into crankshaft (single cyl, boxer, v-twin, inline-4 etc), various rpm power characteristics and gearing affect the traction of rear wheel on different surfaces of the road. That's the reason why offroad machines are still single cylinder or twins, not inline-4 or v-4 like most of street bikes are. Reason is the same - loose surface like gravel or dirt requires different traction and engine's physical features compared with smooth tarmac, single cylinder and twins have less piston strokes per rpms, and also they have better lowdown power due 2 pistons replace 4 - 2 bigger pistons move more slowly compared with 4 small ones having the same stroke and thus they are more easyer to tune for low-rpm power (indeed never look the peak power, but the curve's shape that matters!).
Altough there aren't many bikes like my good R1100GS having more torque in numbers than horspower (101Nm of torque @ 5250rpm and 80HP @ 6750rpm) but i'd gladly give another 20 horsepower away to move that 100Nm of torque into lower 4K rpms - you can feel the need for low-rpm power riding the gravel roads we have here in Estonia.
Also more low-rpm and flatter-curve power makes driving more comfortible - you don't have to revv the bike and don't have to swich gears that much to get it really moving, less stress for engine if working on lower rpms means more reliability for engine. BTW, there are numerous guys converting their R1100RSes airboxes intake tubes with GS ones just to have few extra Newton-metres of torque in mid and low part (in cost of cutting the power from high-rpms of course, but how often do you need the redline power anyway?) - that makes a lot of difference even in everyday driving - more comfort in driving if having more low rpm power and flatter powercurve!
Indeed, gearing is another rocket science field in motorcycles, that can turn into writing 500 page books about here...
But if to leave gearing aside then in conclusion, the RT, S, ST are tuned for more tarmac while the GS is tuned for to make compromise between tarmac and loose surface (so called "dual purpose") to have optimum performance and driving comfort in both worlds.
But, i really find the Swiss army knife more usable than the household or cow-killer one!!!
