+1 on Stelvio comment, the Bormio side is better - but neither are a good "ride" as such, the main attraction is ticking it off your "Biking Roads to ride" list. The views from the top are the best bit IMO, how you get there and back is all much of a muchness for me, the Umbrail is a very decent way back down.
The Splugen seems to be suffering from "Improvements", I last rode it in 2010 and really enjoyed the rugged nature of it, the Italians appear to be trying to make it far more accessible and seem to be ruining it in the process, and encouraging more tin boxes to drive up it. However it is still a bit of a faff and unlikely to be overly popular with your pillion - except maybe the flat bit at the top by the lake.
You have a few options here, you could do all of the Stelvio (And having come up the "nasty" ramp the Bormio side will be a joy) from Bormio there are many options, here is a couple of ideas:
1. Drop down the West ramp of the Stelvio and on to Tirano, then go back up the Bernina pass to St Moritz, onto the Maloja pass to Chiavenna and on to Como.
2. After the Stelvio take the Gavia Pass (SP29 heading South) - this is narrow and a bit rugged, but also extremely scenic, from here you would probably have no option but to run along the SS39 as time will be too short to go back up the Bernina and over the Maloja, but the Gavia is well worth the effort, despite being rugged and bumpy the Mrs liked it when she was on the back - but not so much when doing the hairpins at the Southern end on her own bike this year.
Option 1 = Mainly smooth and easy riding
Option 2 = A few more bumps, maybe worth it for the Gavia - but the Bernina is a right rollocking ride.
The Splugen seems to be suffering from "Improvements", I last rode it in 2010 and really enjoyed the rugged nature of it, the Italians appear to be trying to make it far more accessible and seem to be ruining it in the process, and encouraging more tin boxes to drive up it. However it is still a bit of a faff and unlikely to be overly popular with your pillion - except maybe the flat bit at the top by the lake.
You have a few options here, you could do all of the Stelvio (And having come up the "nasty" ramp the Bormio side will be a joy) from Bormio there are many options, here is a couple of ideas:
1. Drop down the West ramp of the Stelvio and on to Tirano, then go back up the Bernina pass to St Moritz, onto the Maloja pass to Chiavenna and on to Como.
2. After the Stelvio take the Gavia Pass (SP29 heading South) - this is narrow and a bit rugged, but also extremely scenic, from here you would probably have no option but to run along the SS39 as time will be too short to go back up the Bernina and over the Maloja, but the Gavia is well worth the effort, despite being rugged and bumpy the Mrs liked it when she was on the back - but not so much when doing the hairpins at the Southern end on her own bike this year.
Option 1 = Mainly smooth and easy riding
Option 2 = A few more bumps, maybe worth it for the Gavia - but the Bernina is a right rollocking ride.