iFLY or ProSim

Before caughing up over $500 on either of these I was wondering what is the difference?

My understanding...

I fly cockpit builders eddition 1 plane one Panel system.
CANNOT USE WITH OTHER AIRCRAFT. Or can I ...?

ProSim Suite/display.
System should work with other AC? some limited maybe... can I use the display part of suite and fly some compatible 777 or an Airbus..?

What I'm trying to accomplish is get a program that can run gauges on networked PC and display them on my cockpit monitors.
Aircraft I like to use level-d 767, pmdg737ngx, pmdg777 when it comes out... some a320, 330,340...

big problem is FAX cannot run on more then 4 configured displays I tried everything it just won't, crashes every time..
so what's everyone's opinion? I know it might not be too realistic flying A320 with b737 looking cockpit, but that's OK I can live with it just need to invent other sets of sioc scripts for other AC to work so far I just use pmdg737.. but with price of prosim going up.. might be a time to consider something
Thanks
Andy
oops wrong forum I guess sorry