go m3 b/c you can move around in the engine bay...
you have to drop the subframe of a 3zx to get comfy workspace, and you have to trim and be careful puttin in bigger turbos b/c the space is soooooo tight...
go for the m3 b/c you dont have the fixit/upgrade headaches...
and hicas is expensive to fix... (the rear steer option) it also weighs alot...