Maybe this review will help you decide a little more.  
http://solaraguy.org/viewtopic.php?t=21513
As the others have said.  All 3 of these are full Cat-back systems which means it replaces the stock mid pipe.  
The only diff is that now the Apexi WS is a full stainless Steal Pipe while my EVO-I wasn't.  But i say its all Personal Perferance.  I personal like the WS from my experience but others can say differently.  I'm just not a fan loud exhaust systems.  I stuck with the Greddy for a while but in the long run it just started to get to me esp since i drive 52 miles round trip to and from work.
Also on my car the Apex-i WS sit really clean.  Ill try to get some picture this weekend on how mine sits and let you be the judge of it.