On our first property, we looked into a STR specific PM and had little success. We talked to a few PMs based on referrals of other owners. As we talked to other owners, they really touted how great their occupancy was. I saw what their rates were and they seemed low. Once I reviewed rates of other self-managed properties in our area, I quickly understood that the PMs get paid no matter what and the more they booked, the more they made so it was more important to get the property booked at a low rate as that guaranteed income for them.
I personally think its also a strategy that Airbnb and VRBO employ with their algorithms. I'm primarily on VRBO and I get these regular suggestions from VRBO that state "adjust your rate based on changing market data". Take a look at this real example I got today.
Thats a HUGE discrepancy between what I have it set at. We will get those rates all day long in July and they want me to adjust to $100? We also know that most of our bookings take place within 45 days, so to adjust down over 2 months in advance makes no sense. I feel PMs may do the same thing.
This is not a blanket statement with PMs as I have no doubt there are many good one, I just know that nobody will maximize your profits as much as you will yourself. My son helps me monitor our rates on a fairly regular basis and we do very well.
As @John Underwood and @Kenneth Garrett state about VRBO for the Premier status, we do think it has helped us. We are almost always in the top 5 of search results out of approx. 90 rentals in our area. This is due to a combination of premier status, number of reviews and also VRBO has a Boost system where you earn points and you can boost your position for certain dates. This first cabin we only list on VRBO and the 2 new ones we have seem to be getting traction on AIrbnb (I can't explain it) so we're working on their superhost status.
Hope this helps a bit!