It depends more on the quality of the names imo. I didn't have lot of names, but I had some good ones and they gave me a account.
The problem with their opacity - Traffic Z's that is - is that you never know what the deal is. I own a fairly large portfolio and submitted about 20 names to them. I cannot get a reply about the status of the account. If it is the mix of domains, I can provide others. I am not, however, going to put names there that are producing on other parking services.
They need domains as much as we need parking.
From my perspective, it is simply unprofessional to not respond to emails, not participate in industry forums, and treat their service like some sort of God, and I do not do business with people that behave in such a manner.
Fabulous has some pretty clear guidelines and expresses them professionally. Traffic Z is simply unprofessional. And, I would never trust a company that conducted business unprofessionally.