The Laser Rifle crits aren't more powerful; honestly, the two weapons do almost identical damage on normal hits and crits. The difference lies in their crit chance multipliers: the Laser Rifle's is 1.5x, while the Ratslayer's is a whopping 5x. It's hard not to crit with the stupid thing.
The only thing I can figure silent93 means is at 1.5x, the Laser Rifle still has above baseline crit chance, and laser weapons in general have perks to boost crit chance.
Queue
The 5X crit rate is kind of worthless on the Rat Slayer. The gun is really only good for one purpose - Sneak Sniping. Which auto crit anyways. It svcks in VATS with the huge AP cost, and it has a slow rate of fire free style.
The Laser Rifle is extremely powerful. It is a slightly weaker Marksmen Carbine. Fires Fast and accurate. Zoom in and start hitting the fire button!