I've heard good things about the R100GS as well, but I've never had or been on one;. as it's a lot newer than my R90S and the earlier /5's I've had a ride on (they weren't mine), I can imagine they handle better than the earlier ones, like my R90S. I have fitted new rear shocks, progressive front springs, BT46s, replaced the steering damper + the worn mechanism, and fitted different brake pads recommended by a BMW specialist. They all help, but honestly, the Laverda owns it on handling, with my riding style, at least (I'm no Helmut Dähne!) Won't compare the Laverda's drum brakes to the BMWs ATE twin-disc system, but my old V50 with it's small Brembo brakes did a lot better, though (it was obviously not as fast, 5 years newer, and lighter, too). Probably no coincidende those American racing R90Sses had a ton of modifications done to them.
I joke a little on the R90S, but I've had it since the early 2000s, when I took it for a test ride I was sold, not really by the looks (I'm not a fan of the fairing, even if it works well enough) or handling (it still had original soapy suspension, and the brakes had been stuck so the pads were rock-hard/glazed) but by the seating position and torque, and even way back then, the price was good and the basics sound. Having had it for so long the good things outshine the quirks, it's seen more than a few different areas in the past years. If it had not been that our family-piece Laverda came up for sale I would have still been happy.
For length and bikes, it is subjective, as it also depends on your body anatomy of course (length of your limbs etc). I felt cramped and sore on that 750S, but my fathers Le Mans III felt a lot better, as did the 1100 Sport he also had for a while. I'm too much of a realist to be an immense fan of anything, but Guzzi's, like the BMW and my childhood-Laverda, do have a special place for me

I've covered a lot of kilometers to and from work (160km round trip, each day, for years) on that V50, it never let me really down in rain, snow, hail or sunshine. Niggles and maintance, sure, but that's about it.
I had to sell it to make room for the BMW -truthfully it was mostly clapped out after all those kilometers and needed a good overhaul and renovation. I also changed jobs, meant I worked at bicycle-distance, but still kind of regret selling it.
I fitted different handlebars, and altered the brakes from "integrated" to conventional, it was a small-ish but really nice handling little bike which made me, size-wise, look rediculous too.
I never regretted getting that BMW, even if it made me the laughing stock for my Guzzi, Honda and Yamaha minded friends and family members! -a 25-ish years old getting a greybeard-bike
We are getting a bit off-topic from the gorgeous looking MV's though!