[Kriegson]

As hamma pointed out, the factions are usually fairly balanced when it comes to the polls.

Like most have said, the TR and the NC are fairly relatable factions to most people. The totalitarian regime that rules with an iron fist, and the sympathetic rebels who fight for their freedoms (Some anyhow).
The VS are the odd men out in regards to aesthetic, story and weapons. I would think they appeal to a certain niche, while NC and TR are more widely so.

As for some generalized pros and cons for each faction's weapon style:

TR:
High rof and low accuracy play well into a run and gun style, good for assaulting and ambushes.

They do however require you to be exposed while unloading damage onto an opponent. Harder to fight with full effectiveness at range.

NC:
High damage and good accuracy play well to juking behind cover and defense in cover. Minimum exposure with maximum damage.

Missing shots greatly increases your time to kill. You must be accurate, and this makes things difficult in a close quarters run and gun.

VS:
No weapon ballistics and strangely "behaving" equipment makes you difficult to predict. Like hover tanks that can strafe and scythes with their insane mobility.

Aside from the unpredictable and unique functions of their equipment, the weapons are fairly modest in regards to kill capability. Not really outstanding in any regard, but with their own quirks.

-As far as I figure things.