Well a few things really
Firstly, not getting a1 until level 6. Are you insane?!
Secondly, that's 1 too many upgrades.
Jp > Shotty lvl 3
Hell, IMO, HMG lvl2 > Shottie lvl3. Only for hive killing are shotties better.

Headphones only give information of your imediate locality.

Yep. JP's are too hard to devour, and it isn't worth devouring a LA marine. Assuming you have resupply, the only advantage you get from HA is immunity to spores, which isn't worth a whole lot when you have to get past fades and onos.

ok these are my sides of the argument.

i hate getting armour because if i am not playing with a teamate that can weld and not being able to weld myself i think its not worth it.

id rather like to have the firepower to kill them before they get me. OFC I adapt to the situation at hand and the map.

Secondaly. about the hmg > sg. like i said i adapt to the surroundings. if they have onos's . if the map is very narrow at points. i mite get the hmg tho i rarely do.
i prefer the sg as it has a much better reload time which is invaluable in co maps as they are very small, its more than likeley wen ur in the middle of reloading a skulk will leap and bite u.

JP is good but u hav to upgrade armour levels which i dont see worthwhile in public co maps.

....bad bad logic. You are SO much more likely to survive your first encounter with a skulk if you get armor 1. You get 3 bites instead of 2. 50% increase in survival time is a good thing.

Not to mention, if you don't get armor1, and someone DOES get focus, you are officially tissue paper. Armor1 makes focus almost ineffective. The only time focus is useful after the marine team has all gotten armor1 is if you have a lerk sporing armor off.

And umbra reduces all bullet damage by the same percentage, so how exactly is it a "counter" to hmg but not shotties? Unless you meant gls....in which case a good fade is counter enough

At the start of the round, you'll most likely be grouped together with 3-4 other marines so the chance of you getting bitten is minimal. Plus, it's not that hard to just hold a choke point from a distance - you have plenty of time to kill the skulk before it gets near you.

If they have focus (lvl 3) it means I would have a shotgun, fastest finger first. If there's more than one focus skulk, then I'll prolly get armour1 at lvl 4.

Umbra counters hmg by decreasing the effectiveness of the gun (blocks 1 out of 2 bullets). At least with a shotgun you have a chance of taking out the alien if the other team does umbra.

Trusting a group of random marines I don't know with my life is something I won't do. Besides, you can never check ALL the hiding spots; the chances that a skulk will get the drop on you once is always there. Without armor1, an ambush is almost always fatal. With armor1, your precious teammates will have enough time to react and kill that skulk, or you could just jump around and kill it yourself.
And combat maps aren't supposed to have long corridors or chokepoints. Chalk up big rooms without cover to poor map design *cough*sava*cough*. A chokepoint implies that you are defending the chokepoint, which is the aliens' job anyway. Against good aliens, you won't be able to just camp a big room and wait for kills.

In all honesty, you have a better chance of surviving that focus skulk's attack if you get armor1 and resupply, or armor2, instead of a shotty (I'd get resupply). If you can't kill a skulk in the time it takes him to bite you 3 times with focus, no upgrade is gonna help you.

And umbra "counters" a shotgun just as effectively as it counters a hmg. It decreases damage from both by 50%. The only difference is that a shotty is overkill for lerks and skulks up close, but there's really no way a lerk can umbra well enough to protect a rushing skulk from an hmg's longer range, so the point is moot. Umbra helps fades and onos; everything else dies quickly enough that doubling the number of bullets needed only increases the time it takes to kill it by a second or so.

That highlighted bit is key. Jetpackers an make excellent rambos which in Combat is excellent. HA require teamwork. Odds are as a slow, grounded HA you'll get hit a lot. You need at least one buddy to cover you and help you weld up and stuff.

I disagree. JPs die too early on pubs.

Hmm. Well, in a pub, where JP pros are like gold dust, HA can be viable. However it's more expensive to kit out a HA train to shottie down a hive than it is to jet to it, ninja a PG and then just send vanillas through. (A popular PCW tactic.) If all 5 marines empty a shotty clip into the hive it's already as good as dead.
HA is great if your team will weld each other, but otherwise pointless. The tendency for them to group together tightly means that shotties hit more friendlies than skulks, allowing a 3 skulk pack to do serious damage to that train of yours. Additionally, one decent onos makes short work of any HA train. Stomp, digest, run, repeat.