View source for Blaster Launcher vs Disruptor Pulse Launcher

The Disruptor Pulse Launcher is nearly identical to the Blaster Launcher with a few minor improvements. Weight for the weapon is decreased by 4 points and the damage increased by 10. However, when carried in the usual loadout of 4 bombs, the effective weight remains the same since the ammo weight is increased by 1. The biggest drawback is the inability to use this on land (though nothing stops you from loading a ship with it) or during base assaults. Then again, the aliens can't use it either under these conditions, so this limitation is also an advantage.

The most noticeable tactical difference between the DPL and the Blaster Launcher is that the latter weapon usually takes down any alien with a single direct or nearby hit. In TFTD, this is ''not'' always the case. Lobstermen always survive the first hit, and may even survive two. Tasoths may barely survive a direct DPL blast (although it's unlikely), and Xarquid may survive a nearby blast (although not a direct hit). All other aliens are killed if caught in the blast radius. 

The main practical "improvement" is that in the endgame, many aliens will be equipped with the DPL, allowing you to deploy it as a standard weapon.