tl;dr version for you is that turrets require the same skill point investment as other weapons but have much lower DPS and many more limitations/downsides. I spawn in 25 feral bikers and mow them down with various weapons, only allowing AP ammo for marksman rifle (since that's the entire thing of perception tree guns really). M60 clears the group in 35 seconds, Marksman Rifle, SMG, AK clear the group in 50-60 seconds, Pump Shotgun clears the group in 82 seconds, Turrets Clear the group in like 113 seconds.
So IF handheld turret wasn't absolute garbage and IF you didn't have to manually pick up and reload the turrets at full spec your killing power would be between Shotguns and everything else with 3 turrets (2 placed + 1 handheld). But as is turrets lag woefully behind everything else with both more limitations and DPS that is almost 50% less than the next worst contender.