Arbitration can be of a lower standard. The arbitrator will probably be a lawyer, but not a judge. And standards of evidence can be much lower.
I doubt that there are many arbitration companies siding with someone just to get repeat business. That might depend on the scale of business though. For two small businesses, I can't see how it would be a big deal. If a company the size of IBM nominates an arbitrator, I might be suspicious.
Arbitration has its place. Maybe it shouldn't be legal to have mandatory arbitration clauses in employment contracts, or in other contracts without genuine negotiations of the terms.
A non-negotiable clause for a contractor going to Iraq is a whole world away from two companies negotiating a contract to construct a web site or something.
The Arbitration company has a tendency to rule in favor of whoever is going to bring them the most repeat business.