It all depends on what types of domains you have and where your traffic comes from. To simply make such a statement about any parking company just shows inexperience to me. With perhaps the exception of saying Sedo is the worst parking company.
Exactly. Different parking companies are good for certain domain types and sources of traffic.
For example, finance-related domains perform really well at ND. Or should I say extremely well! They pay the best for these. CPC is $2-$6. I once made the mistake and removed them from ND, and lost quite a bit. I get the best payouts from ND, but then again, I have more financial-related domains in my portfolio. They also pay the best for African traffic- even for non-financial domains, e.g. technology, sport.
You got to know where to park certain domains and the source of the traffic. You can't just choose one parking company-you will throw money away like that.