Hi Andrew

The BOINC version of cpdn has been running since about 2003/4.
At that time there were only a few other projects, and some simple climate models, and the credits were made compatible with SETI.

Since then, lots of other projects have appeared, all with their own ideas about credits. And then there's GPUs, with their faster crunch speeds on some projects, and therefore more credits per unit of time.
Occasionally, some of the new model types here get the wrong amount of credit per unit of time, but this is easily fixed, so as to keep all of the model types consistent.

cpdn has no intention of trying to work out what a "better" credit rate is, based on what other projects do. People have to take us for what they find.