i'm in the same boat is micah, i had (until last month) a legnum super vr-4, and my ex had a series 1 stagea.
stock for stock, and even into the light mods, a legnum is a quicker, more agile car..
my legnum ran a 13.7 1/4 mile with 3" cat back and 12psi only, and was pretty good around corners for a wagon
but the stagea has more aftermarket parts, and they are cheaper.
the stagea is also quite a bit larger, you notice it most in the front seats.
in the stagea you could swim in the foot wells, the legnum was definately a bit more lacking in the leg room (that said it's not small)
i enjoyed my leggy, it was a great car, pretty reliable apart from a blown gearbox (i was at the drags at the time, but who knows the history of the car), could get 10L/100km if i cruised around, and got even less with country runs.
but then a S1 stagea dumped with decent rims also tickles my fancy too.. my ex managed to get 10L/100km from her modded stagea too, so really it comes down to how you drive it, the legnum would chew more fuel than the stagea if both were given a boot though.
go take them both for a test drive, and go from there.