Micro and small business are a little less satisfied with their main bank over recent months, research into customer satisfaction by DBM Consultants shows. Bigger business, by and large, are a little more satisfied than they were.Commonwealth Bank may be making further headway in the micro business segment and at the expense of ANZ, the DBM research shows.Over a survey period that covers this first six months of 2010 CBA ranked marginally higher than ANZ for the first time in the DBM research. DBM uses a ranking scale of 1 to 10. CBA rated 7.0 in the latest survey and ahead of ANZ and Westpac at 6.9.DBM consider the sample size of 4000 allows it to draw a statistically significant conclusion that CBA ranks ahead of the other two banks, despite the fine margin in the rankings.ANZ used to rank just ahead of CBA in the DBM ranking on business customer satisfaction.Due to the newness of DBM's syndicated research on banking the findings so far cover only major banks. The firm expects to cite findings on other banks once the data set on small banks builds up.For more on DBM's research methods, and wider issues in researching business views on banks, see the next article.