Reviews at the time said Mag 21's were good performers suspension wise, fairly light but imprecise in steering (mentioned above about the stiffness of spaghetti), the Marzocchis were precise, but heavy and the suspension action was poor. The conclusion was that the Manitou 2's offered something between the two and were the best compromise.
It's why when I bought my Claud Butler I tried all three on different bikes and opted to have the Marzocchis removed and a set of Manitou 2's fitted. Ironically it now sports Marzocchis but much later Z2 Atombombs.
Carl.