Mass Effect 3 lets you choose between an effective gun build and a powerful biotic build. In general biotic powers are much more powerful than guns, but some guns, like the sniper rifles and shotguns, are very fun to use. The machine pistols can be specialized to weight very little and often times classes get weight bonuses that let them use some machine pistols anyway. I haven’t found any machine pistol that I would use over a heavy pistol though.
Why You Have to Choose
Any good gun, like the geth plasma shotgun, the claymore and most sniper rifles, area very heavy. In Mass Effect 3 the weight of all the gunes determines your recharge bonus. It ranges from -200% to +200%. Generally you can only carry a heavy pistol and some machine pistols without incurring a penalty to the recharge time.
What is Better?
Guns are fun to use and some are very effective. But, as soon as your gun isn’t right for the circumstances, it becomes much less effective. For instance, a slow firing assault rifle is much less effective versus a shield than a rapidly firing machine pistol. Overall you can’t be as aggressive with guns because your health and shields, especially in the silver and gold challenges, is very low. Your health only regenerates partly depleted health bars which means that you have even less to play with.
It takes time to unlock the good weapons, and regardless of what pack you choose it is random when you unlock specific weapons.
Biotic powers are much more effective than weapons. As a vanguard I can take on any number of enemies at once and kill them very quickly. Usually teammates use guns over biotic powers, and whenever I play as a vanguard I outscore everyone at least 2x. I have had around 100 000 points when my other teammates had only around 20 000.
Boss fights are very hard to finish with weapons, not to mention Reaper boss fights which are basically impossible with guns unless you wan to take 10 minutes to finish each of the later waves.
Biotic powers let you be very aggressive. If you haven’t seen a good vanguard play I suggest you check out dinoridingjesus and xcalizorz on YouTube. They have some very good gameplay on their channel showing how powerful biotic powers can be. Anyway, the vanguard is only one example of how you can be aggressive with biotic powers. The energy drain of the salarian infiltrator lets you have similar game play. If you specialize overlaod so that it can hit 3 enemies at once and stagger them the engineer can be aggressive as well.
So it is clear that biotic powers are much more powerful and reliable than weapons are. Whenever I see teammates using a lot of weapons I know that they are going to end up at the bottom of the scoreboard and contribute little to the team.