Both are ABS plastic and the same material as TM/JG as far as the guns I handled last year.
I don't know if that has changed in 2009 with the cansofts.
SRC has metal cocking handle and it's on metal mag release catch and a metal hop-up.
As far as internals, both will be using ball bearings in their bushings and otherwise both are similar. I would say go for SRC.