ME1 Weapon Comparison

The “damage” stat on the weapons in the first Mass Effect game is actually the damage per second (DPS) stat.

Therefore, we can compare all the weapons types in terms of their base DPS. The following is the DPS on the highest rank of Spectre weapons:

HMWA X (Assault rifle): 384 DPS

HMWSG X (Shotgun): 378 DPS

HMWSR X (Sniper rifle): 336 DPS

HMWP X (Pistol): 294 DPS

With no skills, the assault rifle (AR) has the highest DPS. But, the pistol's marksman ability (unlocked through the pistol talent) increases the rate of fire of the pistol for its duration. Master Marksman (12 points in pistol talent) increases the rate of fire by 2 rounds per sec. Without marksman, pistols fire at about a rate of 4 rounds per second.

Thus, the DPS of the pistol with Master Marksman is,  294 * 6/4 = 441 DPS. This is higher than the AR's DPS. If you can keep Master Marksman activated 100% of the time, it will certainly do more damage over time than the AR. 

Therefore, including marksman the DPS chart becomes:

HMWP X (Pistol) with Master Marksman: 441 DPS

HMWP X (Pistol) with Advanced Marksman: 404 DPS

HMWA X (Assault rifle): 384 DPS

HMWSG X(Shotgun): 378 DPS

HMWP X (Pistol) with Marksman: 368 DPS

HMWSR X (Sniper rifle): 336 DPS

HMWP X (Pistol): 294 DPS

Keep in mind that the sniper rifle and shotgun can do more damage on their first shots with the Assassination and Carnage abilities. Depending how long you fire, they may have a higher DPS than the AR or pistol.