You're right, apples/oranges. The only thing about a Sportster is if you're over 6', they're a little small for long trips, whereas the Lowrider is roomier and rides better.Close enough to a Super Glide Yes. Step up from a Sporty, nah. No more than an apple is a step up from an orange.
In Harley marketing it IS a step up but I'm one of the " I never wanted a Harley but, I always wanted a Sportster." guys.
And that's a good looking bike!