Business & farm

Am I correct in understanding that if I enter a computer purchase as a Miscellaneous expense w/ description "safe harbor", then I don't enter it as a 179 asset?   What are the pro/cons of these two approaches - assuming I want to expense the entire asset this year?   I'm a bit confused between the differences and whether I need to complete a form to indicate 179 asset if I enter it under Misc business expense.  Will you please clarify for me?  Thanks.