The 5-147278-5: This is a 6-position, single-row header on 2.54 mm pitch — the standard 0.100-inch grid that matches legacy board layouts and common IDC ribbon cable.
Mating interface and plating grade
The key difference: 5-147278-5 uses gold-plated mating contacts (15.0 µinch) and SMT termination, while 1394090-1 uses tin-plated contacts and through-hole termination. If your board requires SMT assembly and gold for high-cycle reliability, 5-147278-5 is the correct choice; if you can use through-hole and tin is acceptable for your duty cycle, 1394090-1 is a cost-optimised alternative.