http://www.ft86club.com/forums/showthread.php?t=103674
Both of these vent pressure. The rear vents more or is more directly connected to the block. That one has a check valve because of where it recirculates gases to and where it comes from.
All FI applications will increase blowby gases. Managing that excess blowby gases can be done with a catch can that is vented to atmosphere or one that is closed, which may be necessary for emissions. You could not do catch cans and just upgrade your PCV valve to a WRX one from a FA20DIT motor, but you will likely see more crap collecting in the intake.