While I don't have a 1250, I have a competitor in a CBF1000 with similar specs. The difference in your 650 Versys and the 1250 will be huge. I had a 650 Strom and it's a very capable motorcycle, but with full luggage and passenger, it took a lot of the performance out of bike, and fuel mileage really suffered. You're probably feeling similar with your Versys in similar circumstances.
Same luggage and passenger on the bigger bike, it doesn't care. Fuel mileage don't suffer and and as the rider you hardly feel your carrying anything.
You'll love the 1250, and adding luggage, especially the trunk, is very simple.
Don't sweat the petty things; Pet the sweaty things !!!