Clin Chem. 2004 Sep;50(9):1678-80.

Ståhlberg A, Kubista M, Pfaffl M.

Comparison of reverse transcriptases in gene expression analysis.

Estimate yield by using reference DNA and RNA molecules of the same sequence. Best: SuperScript III; worst: AMV. cDNAs were reverse-transcribed at the temperature recommended by the manufacturer, so this is probably a confounding factor.