Sonic Pistol vs Sonic Blasta Rifle
The comparison between Sonic Pistols and Sonic Rifles comes down to a matter of efficiency. In a situation where Sonic Rifle clips are in abundance, using the Blasta Rifle as a mainstay weapon is an extremely effective choice even until the endgame, due to the fact that they possess just enough extra firepower over a pistol to bring down tougher aliens in a single round of fire from one soldier, and do so with an extremely high degree of accuracy. Pistols are effective, but not as effective, except when fired far more often, due to a slightly lowered damage and accuracy. Both are excessively strong against Aquatoids, but against Gillmen the Rifle's increased firepower gives it an edge in efficiency. The advantage both have over the Sonic Cannon is increased rate of fire. You can rarely expect to get more than a single shot from a Cannon per turn, and on most targets that single shot is either overkill or not quite enough, and multiple shots from the weaker weapons actually provide more firepower per turn.
In total firepower per turn, with minor movement, you can expect three snapshots from a Pistol, two from a Rifle, and one from a Cannon. In terms of accurate fire, the rifle provides slightly better accuracy while allowing for minor movement, and also offers an extremely accurate Aimed shot. The Blasta sits between the accuracy of the Sonic Cannon and the raw per-turn firepower of the Sonic Pistol. Depending on the accuracy of the soldier in question, either of the two extremes may be preferable, but the Rifle is a dependable and accurate, with enough shots per turn to account for a miss, and enough accuracy at a low TU cost to give the mobility needed to fire from cover.
Rarely does the supply of Blasta clips dry up in the conflict. However, should ammunition stores for the pistol and rifle become low enough that they must be engineered, and it is decided not to replace them with Sonic Cannons, it's a common choice to give up the Rifle and make Sonic Pistol ammo instead. A rifle clip costs 2 Zrbite to create, and yields 15 shots in a rifle, while a pistol clip costs 1 Zrbite and yields 20 shots. For the same amount of Zrbite, you choose between 15 and 40 shots, which makes the decision fairly clear as to which is the most cost effective. Even with the Pistol's lower accuracy and reduction in firepower requiring extra shots be taken, that is more than double the amount of shots of two weapons with nearly identical firepower.