Rear I/O on both boards follows a familiar budget-to-mid-range pattern: matched USB counts across Gen 1 and Gen 2 Type-A, four USB 2.0 ports, and a single RJ45 jack. Neither offers Thunderbolt, USB4, or eSATA, which is expected at this tier. The meaningful split comes down to two specific choices each manufacturer made in allocating their remaining port real estate.
The Gigabyte B840M DS3H prioritizes display output breadth, pairing HDMI with two DisplayPort outputs — giving it three simultaneous video outputs total. This is a tangible advantage for multi-monitor setups driven by integrated graphics on a future APU, or for use cases requiring flexible display combinations. The MSI Pro B840M-P Wi-Fi6E takes the opposite trade: it drops DisplayPort entirely but adds a USB 3.2 Gen 2 Type-C port running at 10Gbps, which is genuinely useful for fast external SSDs, modern peripherals, or connecting to a USB-C monitor via adapter. The MSI also ditches the Gigabyte's PS/2 port — a legacy inclusion that only matters to users with older keyboards or mice, but irrelevant to the majority of modern builds.
Which board wins here depends entirely on use case. For multi-display productivity or APU-driven setups, the Gigabyte's dual DisplayPort is a clear advantage. For users who need fast USB-C connectivity at the rear panel, the MSI delivers where the Gigabyte offers nothing. Neither board is objectively superior — they reflect two different philosophies — but the Gigabyte's display flexibility is likely to be relevant to a broader range of users.