The 5499160-4: The 20 circuits match the width of a 20-conductor flat cable, so the board footprint lines up pin-for-pin with the mating socket without gapping. At this current the temperature rise stays well within the UL94 V-0 housing material limit, even with all 20 positions loaded.
How the latch lock and shrouding affect your harness assembly
The short eject hooks on the latch lock give a positive click when the socket seats, and they lever the socket off without prying — useful when the connector is buried in a dense harness. A keying slot and mounting flange are built into the housing. The keying slot prevents a mis-oriented socket from being forced in; the flange gives a secondary board-retention point if the assembly sees vibration after soldering.
Active production — sourcing posture
How this header compares to the 12-position sibling 1379030-3
Gold buys you hundreds of mating cycles; tin is typically rated for 50 cycles or fewer. Another delta: the 5499160-4 housing is UL94 V-0; the 1379030-3 is UL94 HB. For equipment that must meet a V-0 flame rating, the 5499160-4 is the compliant choice. The 5499160-4 is vertical through-hole; the 1379030-3 is right-angle.