Accounting calendar selection

I've used a 4/4/5 week convention (1st month of qtr = 4 weeks, 2nd month = 4 weeks, 3rd month = 5 wks, 1-2 day difference at year end is tacked onto Week 52) at some co's, and the regular calendar (e.g. Jan 31 days, Feb 28 days......) at others. Getting the sales, logistics, purchasing, warehouse, other functions to sync up their processes, metrics, is a key issue. Overall, which convention do you think works best for a company that sells and ships tangible product? Not just the impact on accounting and taxes, but the sales, marketing, purchasing, inventory mgmt groups. Any key talking points why? Thanks !