Pretend you're a tenant, show up to some open inspections of houses they are advertising, and see if they treat you like crap or not. Also ask any renters you know who their agent is and if they are happy with them. Things like never passing on maintainence requests to the landlord or just never communicating fullstop aren't good for anyone, you don't know what is up with your house and the tenant thinks you're a noxious tightwad.
I've been treated like a 3rd class citizen by PMs often enough as a renter I'd never use those PMs as a landlord.
Happy tenants are less likely to do bad things to your house.