Re the faction vendors - I can't say that they sell anything of note. I have, however, had a couple of drops that are very interesting that the vendors do not stock (at least I think they don't) A dead orbit arc fusion rifle which feels better than a Plan C and I've barely started to upgrade it - plus a FWC pulse rifle. Basically I have all the weapons I wants to buy, as the drops I've had have been better, anything available for sale is inferior to what I've been given for free...