Autostrade versus Strade Regional?

I have not driven that stretch of road, but I can assure you that the autostrade will be faster, easier and likely more expensive.

I avoid the freeways because the routes can be less scenic. The secondary road will be more challenging but has the potential to be more scenic.

it straighter and easier to maneuver?

If it wasn't straighter, divided and safer nobody would take an autostrada and pay the toll. Everybody would use the free roads.

On viamichelin.com you can see the difference in time on travel simply ticking the "avoid tolls" box on the right

The question makes little sense as there is no highway itinerary from Ortisei to Cortina.
The shortest itinerary is through three high-elevation passes (Sella, Pordoi, Falzarego), extremely scenic but very windy and steep, with a lot of hairpin curves.
If you want a much longer but not as steep and easier to drive itinerary, it could be: Ortisei to Chiusa (very windy but not steep), then Bressanone, Brunico, Dobbiaco, Cortina. There is actually a pass (Cimabanche) between Dobbiaco and Cortina but lower in elevation and without hairpin curves.
An intermediate itinerary would be Ortisei to Corvara (one high and windy pass), then to Brunico (a bit narrow but flat), then Dobbiaco and Cortina as above.

There is no autostrada between Ortisei and Cortina.