The second placement is a better choice from an overall standpoint. In the vertical placement, adhesion is going to be more critical, although Prusa printers have good bonding for PLA and ABS, from my direct experience.
The other aspect of more importance is that the holes are going to be distorted in the vertical arrangement. The cut-outs in the smaller portion will also "droop" unless otherwise supported. If supported, you'll have greater post-processing labor and unsightly surfaces.
The design is quite well done, as the corners have radii which allows for smoother carriage travel, rather than abrupt stops with direction changes at each end.
Importing the model and having the result appear as in the first image means that the designing software swaps the z-axis and the y-axis, which is relatively common.