Open front is direct noise escape path leaking slightest noise out unmuffled.The issue with some cases re airflow is the lack of a semi open dust meshed front. There's so many cases that are decent but let down by front air intake having to rely on side slits to draw in air.
Air again is pretty darn low viscosity fluid and doesn't mind much about doing couple turns if path is properly done.
Of course if fans are some pressure impotent Noctua S12s, then then any airflow impedance is problem.
Though blocking direct noise escape path would also allow increasing fan speed some.