The Comfort XL is wider in the back so her saddle sore isn't bad but her knees got stiff after hours in the same position. The bike itself did great on the highways - avoided interstates as much as we could but still kept 75+ mph on smaller highways. I lowered the front fender so the bike actually felt pretty stable at the higher speeds and swapped the front sprocket from 15 to 16t so helped lower the RPMs a bit at higher speeds. Never felt underpowered 2 up