I don't think I strictly agree with Shin; a firearm provides a different flavour certainly, but I don't think the choice to use one carries that much gravity unless we're talking about an Enforcer.
Firearms aren't all that difficult to acquire and play around with and I certainly don't see them as a status symbol - there almost no barriers preventing people from getting a firearm who apply themselves. On the other side of the fence, you have street-sams who are insane enough to enter a firefight with nothing but a katana and a syringe of vee, that also requires brass balls. Simply using a gun carries little weight; any punk can get a heater and wave it around. Fear factor harassing everymen, sure, not weight. The character behind it and their actions give it weight.
It's true that guns bring unique RP to the table. The same is true of all weapons. The choice of weapon really changes the tone from 'hitman' to 'psycho slasher' to 'hired thug'. You can't play a sniper without a sniper. To break it down further, there's a big tone change from a PopPop to a Walther PPK/s to a H&K Mk23-S. Using a machete screams 'ganger' or maybe 'deranged butcher'. Using a composite katana? Street-sam.
On a larger scale, aside from the individual flavour each style adds, certain professions carry the expectation of using a firearm - or not. Additionally there are different RP opportunities out there that simply don't exist to people unless they're practised in specific weapon styles.
Firearms offer numerous advantages to people who really want to push the mechanics as well as several safety nets. Generally, if a melee character wants to get something done in combat they have to almost fully commit to an engagement whereas a character who uses firearms has more options available and options that can get them out of danger but still able to contribute to the fight in a pinch. Melee weapons have fewer decision points.
For me, the weapon choice on any given character is a 100% RP decision and not out of any want to play around with the individual advantages; my own choices reflect my characters' wants and tastes and not my own preferences. I have in the past chosen to specialise with very sub-optimal weapons and would do again if it fit the character. I think that a lot of players will agree. There are a lot of factors that could lead somebody to pick a certain weapon both ICly and OOCly motivated.