Hardware Verses Software Plugins and Routing

Hardware?  Is it analog?  Digital hardware does have a slight advantage, too, since it is optimized for one task.  But it is the skill of the user more than the type of equipment used.  I like analog hardware going in or rerecording soft synths, and in mastering.  It adds a little something to pure digital, tho I admit digital is getting better and better with saturation etc.

AS far as routing, you want to hear the effect while re-recording, which means coming to the external hardware but not necessarily the signal you are listening to.  That gets recorded, which is what, ideally, you should be listening to.  In sonar I tap a sub out, route that to a hardware out, into my external hardware and then back into in 1/2.  That signal is what I listen to.

@ 

Use SONAR's External Insert Plugin.
 
It allows you to insert hardware units into the signal chain as if it was a software plugin.
 
SONAR will compensate for the round trip latency introduced by this process.
 
As to whether hardware is better than software.
 
The operator will have a greater impact than either software or hardware.
 
I use a pair of external preamps for processing mic/line signals coming into the box. I also have a channel strip for use outside the box but to be honest I'm getting such good results purely ITB that sometimes I don't bother going the extra step.
 
Whatever makes it easy as long as it doesn't compromise the sound quality.