The vigilante grind is definitely much harder than the cop grind. APD have a bunch of rules and in-game mechanics in place that make it a fighting faction essentially. Plus as a vigilante you've gotta watch out for the stupidest shit because one small slip-up someone like Keith the cop will come and reset you back a tier. The two are barely comparable and shouldn't be grouped together when it comes to arrest reward reductions. The only people making significant bank off the role are tier 4 vigilantes who definitely deserve as it's hard to successfully do runs and they've grinded so long for it.