The SDR-5D is one of the few 'Mechs capable of mounting ECM (and the only ECM-capable mech to also mount jump jets). Three energy Hardpoints allow it to take advantage of the lightest weapons available. Its impressive jumping capability is only surpassed by the Spider SDR-5V.
No BattleMech can match the SDR-5V when it comes to Speed and agility. But while it possesses incredible maneuverability, it has very little offensive capability.
The SDR-5K retains much of the mobility of the earlier -5V. It decreases the number of Jump Jets by two and one of the Medium Lasers to add two Machine Guns to the design.