Huayao is a state-owned enterprise, the official website will be the first time to show the national provinces, municipalities, military districts, hospitals, the latest bidding announcements, but also the agent of a lot of provincial bidding projects. For the recruitment, bidding mode analysis and other points more authoritative.
Smart pick was established not long ago, did not act as an agent of other provinces and municipalities bidding projects. Only show the national tender announcement.
Taimao I am least optimistic, because I feel particularly professional, often wrong analysis and information, but also shows the national tender announcement.
Haihong only shows projects tendered by its own agents, without any analysis of bidding patterns.
I hope the above helps.