I did what you said, @Ali Boone, and it's worked well so far for me. I'm in the process of buying right now, but before I did, I spoke with 10 or 11 different Turnkey companies (I started by using @Jay Hinrichs turnkey-reviews.com site) and about the same amount of property management firms.
After all those conversations, it was MUCH easier to figure out the ones who know the area, know the numbers, and have confidence in what they offer. When I spoke with them, I had a preset list of questions I'd ask (though I'd try to do it organically--not just read them off); their responses were telling.
The solid companies would answer quickly, wouldn't hesitate to give me direct answers, and had no problem with me digging deep into why they did certain things (ie why they don't manage in certain areas, or why they purchase in certain areas but not others--and I always wanted facts from them, not feelings).
There was one Turnkey provider that said "That's a really good question" to practically everything I asked... and then proceeded to give dodgy answers to direct questions like "Why should I invest in [city name]?" or "What's your vacancy rate in this particular area?" After that call, hearing somebody say "That's a really good question" more than once became a red flag for someone trying to figure out how to answer a basic investment question.
As a buyer, I'm relying the on the Turnkey to have their numbers in place and their reasons up front. I should never have to pry anything out of them. It's up to them to convince me with facts and numbers to buy from them. If they can't confidently do that, no way am I wasting my time by talking with them further.