Had an 1150GS before present 1150GSA and I loved the GS just as much as I love the GSA, both excellent bikes IMHO.
I found GS was easier round town until I got the seat lowered on the Adv.
I prefer the Adv lower 1st gear, found the GS 1st gear was a bit too high sometimes and ended up riding clutch a bit too much when swmbo and luggage onboard, also the GS's 6th gear was slightly too high for my style of riding, found I was changing from 5-top and top-5 quite a lot, but think it helped give a better mpg. Sometimes I wish the Adv had a higher top gear then remember wishing for a lower one, so still not convinced which gears really best, suppose a 5 1/2 would be ideal top with the Adv low first
Bigger tank better on long runs, but it's dang heavy when full, which makes it hard to put on centre stand. Also don't lean over too far on a slope with with a full tank, you probably wont be strong enough to stop it slowly falling over !
My GS was a 2000 model and I thought quality was slightly better than my 05 Adv, .
Engines seem the same to me, single or twin spark,

twin spark could be slightly smoother but cant remember that far back really to compare.
Similarly with suspension, both were adequate for my riding, both very stable and composed on bumpy tarmac, both feel "planted" and inspire confidence at top end of legal limits. Both really nice to hustle through the A road twisties. I don't go "off road" to any great degree, dirt tracks through Dalby and N Yorks areas on dry days, because I don't want to drop the thing and damage it yet. (I admit I am a woos)
After market shocks and other bling bits would no doubt improve both bikes, but would be wasted on me.
Lights fairly poor on both I feel extra lights are a good investment on both models.
Both bikes really good to ride naked, not me, I mean ride without a screen. Really nice on hot sunny days, well dryish and warmish then in UK.
Well after writing all that down and thinking about the original question, apologies for rambling on, the answer is I wouldn't see it as a downshift and that I would be happy on either really. However in my heart of hearts, I prefer riding the Adv and I can't say why.
Logic, and sore ribs from being prodded by SWMBO tell me I shouldn't because the main reason for preferring the GS is that the GS's rear seat even after the remodelling job on the Adv seat, is more comfy I am told. Also you don't slide about on the GS one.......apparantly.
Then again that could be my riding style, but what the hell........... after all, .............I don't ride pillion.
