Crop vs Stitch Pano
This is a projection issue. There's no perfect way of mapping an ultra-wide scene to 2D. Rectilinear (top) keeps straight lines straight, but expands the edges and turns circular things in the corners into ovals. What you get with stitching depends on the projection the program uses (which one is it?). "Best result" depends on image content and your personal preferences.
Paralax correction with an appropriate leveling head and nodal slide will eliminate stitching problems, particularly if you stay away from the corners of the frame.
My display of mediocrity