Yes, gangs that have been around longer and have had time to expand their numbers, resources, connections, and influence over the city are stronger, you have to find out how to work around that, if youre at war with them you should negotiate peace or try to avoid engagements where you dont outnumber them for example, this is kinda what you sign up for when you fight a more experienced, wealthy, connected organization in the city. and you dont need body armor to cook drugs or win fights.
Lets say Gang A is a new group with light pistol imports, limited members, and not much capital. The cartel doesnt trust them enough for heavy imports. Why should they match Gang B, a well established gang with alot of money and strong cartel ties? If Gang A is in constant conflict, they should consider diplomacy, using certain tactics, or using certain gear. They could also work on building relationships to avoid unwinnable wars. Making body armor widely available reduces the influence larger factions have beyond combat which in turn could reduce a section criminal faction rp to running solely on pvp. Or get body armor of your own, become a loyal and valuable ally to a gang that can get AP and then ask for it they might give it to you.