As far as complexity, series wins hands down.  Jim converted from parallel to series and in the process lost 10lbs of weight, over 2 qts of excess coolant (in the extra hoses), a ball valve, 4 sections of hose and 16 clamps!!! 

        This doesn't necessarily apply in every case. I planned my parallel installation very carefully to ensure minimum weight and even flow and honestly believe I achieved it at no extra cost in weight. I have the shortest possible runs of hose, but if I went to a series configuration I would have to lengthen the inlet hose considerably in order to route it around the turbocharger and intercooler.

        This is not to argue that parallel is better than series, but only to point out that with proper planning, weight doesn't have to be a factor.

S. Todd Bartrim
Turbo 13B
RX-9endurance
C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm

        "Imagination is more important than knowledge"
                                        -Albert Einstein