Killed my head reading that lol... I am not one for noticing names of guns or owt, i just look at the colours and if they look cool
Will have a look at them.
Destiny is more like an MMO than a FPS. As such you can't play it like COD where you just pick any weapon from the list and expect to kill people with it. It doesn't hold your hand like COD does and you need to pay attention to the game mode you're playing in and the stats of your weapon.
If you're playing regular crucible, then level advantages are disabled. Doesn't matter whether you are a level 10 or a level 32, you all have the same health, and given identical guns, will do the same damage.
As such the only stat that matters in crucible is the impact. The Attack value of 365 means nothing in the crucible. Auto rifles will usually have a low impact and take lots of shots, but they can fire faster and be spammed to counter act that. If you are the sort that can aim well, look at hand cannons or scout rifles which will hit much harder, but fire a low slower and with no auto fire. Pulse rifles are a nice halfway house in between. But the golden rule is pick whichever gun has the highest stabllity (ie the lowest recoil and easiest to shoot) and the highest impact.
Destiny players will specifically re-roll their legendary weapons to get the best perk combinations. Eg you can turn scout rifles into full auto if you re-roll them with the right perk. The deadshot luna scout rifle from Dead Orbit will fire in full auto nearly as fast as the slow auto rifles. So picking a precise weapon, doing your research on best perks and re-rolling your weapon to get them are important.
Just picking any random weapon because its purple won't work in destiny. Destiny players will know the names of the guns, the specific stat rolls that can be obtained from those guns and purposefully seek those guns and get good rolls on them. Go up against them in the crucible with poor weapon choices and you'll get destroyed.
When you start playing Iron Banner or trials of Osiris, then level advantages are enabled. This means you are likely to struggle with a level 32 character, and find it really difficult with a character less than rank 30. For these the impact stats AND the attack value AND your character level matter. The rule of thumb here is to do what you do in crucible, but make sure you're as high a level as possible and preferably with your choice of primary in 365 attack form.
Trials and Iron Banner are both end game content for PVP players (Trials of Osiris more so) but you're likely to find lots of players in those with the absolute best combos of armor and weapons possible for PVP. As such the best players will nearly always have one of the best exotic primary weapons : Thorn, Last Word (exotic hand cannons), Vex Mythoclast (Exotic Fusion Rifle primary rewarded from Vault of Glass) Red Death (Pulse Rifle)
Ultimately, destiny is a gear based game. Your weapons and armor play a vital part in how good you can be in PVP.