TruePower: Dedicated circuits for each power rail, SATA connectors, 4 pin connectors for fans (controls speed = quieter computer), fans are double ball bearing.
Smartpower: Standard power rail setup, no dedicated fan connectors, no SATA connectors, sleeve bearing fans.
The SmartPower PSU is still a quality unit that will handle most rigs with no problem, but I'd say go for TruePower if you were making the choice between the two.