Be warned, that I am biased.. towards which side you will soon
find out.
Performance wise, unless you get the STi Spec C, the E8 is going to
outgun the STi. But its about 0-something secs... not much
difference. The E8's technology (according to a PI and others) is
more superior, i.e. if you manage to whip the tail out for an E8,
its quite a feat. Front-mounted intercooler is definitely a better
way to cool the turbo engine (look at the WRC WRX, its front
mounted). According to a pretty famous workshop, the evos are
easier to mod compared to the WRX (this can be disputed). The MR
has a superior AYC plus lighter components and is definitely going
to be a great drive.
Insurance, FC and other necessities (i.e. brake pads, tires,
clutch, etc) are going to cost.