system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek]What is the difference between phasers and disruptors and why does it seem like the federation is the only group that uses phasers?
gpt
It's sort of the difference between a sniper rifle and an AK. The sniper rifle is more elegant, accurate, and effective, but also costs more and is harder to maintain, requiring pretty good supply and maintenance support. It's also greedier powerwise. If you're a naval officer, you want a phaser. If you're going to be stuck on some shithole planet for awhile with no support and you're mostly interested in protecting yourself, go for the disruptor instead.

Both use energy to manipulate matter in the target zone, but do so by different methods. The disruptor crudely and violently agitates molecules in the target in order to disrupt its molecular cohesion; for soft bodies, this produces haemorrhaging and tissue ruptures, broken bones, torn nerves, and so on; it's effective, but in the way a rusty axe is. A phaser changes the energy state of the target zone, and can do so very precisely (depending on design; not all phasers are designed with such precision in mind). A phaser can deliver a usually painful but only momentary and rarely dangerous shock to the nervous system of the target, causing a temporary loss of voluntary muscle control and (usually) consciousness. At the highest settings, it energises molecules so much that they transition into plasma, which quickly dissipates as energy into the immediate environment, effectively dematerialising matter in the target zone. (At the highest setting of all, the phaser produces an internal feedback energy buildup, until it spontaneously converts a large portion of its own matter into energy all at once, effecting a surprisingly powerful atomic explosive, but one that's also effectively uncontrollable. As a 'weapon,' this option is pretty dangerous for user and target alike.) At the same time, a skilled phaser operator could weld, cut, or even perform surgery with a phaser (if it's of a sufficiently sophisticated design). It's a lot more versatile than a disruptor, but that comes at the cost of higher demand on quality construction and technical support, and a somewhat higher demand on power.

The shortest answer to the question of why so many non-Federation powers prefer disruptors is the same reason the Soviet Union favoured the comparatively crude Kalashnikov over the technically superior M16: It *gets the job done*. It gets it done messily and brutally, and usually quite painfully, but it gets it done. And best of all, it's relatively efficient on power, relatively inexpensive, relatively reliable under harsh conditions, and so on. This is a cultural difference, but also a practical difference; disruptors are just easier to deal with over the long haul, a lot less hassle than an arsenal of fussy and needy phasers.