Preferred how strongly? Eliminating the failure mode in this case means designing a whole new wing from scratch, which is nearly the same amount of work as designing a whole new plane from scratch. So Boeing's alternatives (while maintaining the same efficiency) were to completely replace the 737, or fix the issue in software. The latter option is obviously vastly less expensive. If you're confidence in the software fix is high, it's probably a reasonably choice. In hindsight Boeing's confidence may have been misplaced.