To be fair, lasers are a LOT more common and seemingly practical in Star Wars than railguns and kinetics. That said, based on how they're commonly used, they are the exact opposite of a light, easy-to-aim weapon. Well, maybe they are potentially easy to aim, with the OG-9 being basically the spinal laser prism Warmachine was proposing in ground form. Though that and the LAAT/i seem to be the exceptions rather than the norm. (SPHA, B-Wing prototype, Death Star superlaser...)
However, laser weapons in Star Wars seem to be limited to giant, screw-that-one-guy-in-particular weapons that are more of a vehicle built around a gun than a normal weapons system. Also unlike railguns, they are actively being developed in Star Wars, with the proliferation of composite-beam lasers during the Clone Wars.
Given that an OG-9 is basically a supersized Gonk Droid with giant legs and a tiny anti-personal blaster outside of that laser, my guess is that laser weapons are insanely energy-intensive. If I had to take a guess, they're more efficient at dumping energy into a target, but require a lot more machinery space and energy due to not being able to use Tibanna gas.