I would say it has to do with your audience. As a developer, I would want to see the errors on the sheet as they are calculated. This way I can work on reducing or removing the source of the error, rather than just hiding it. If it is a report for users who have little to no Excel skills "Not Found" is so much more informative than "#N/A".

If it is a question of performance, then go for the path of least amount of calculations. If it is for presentation, calculation time doesn't matter (as much). Of course, IFERROR() solves the issue of double evaluation, as long as all users have 2007 or higher.