Blessyou,
In my set up, the speaker wire route is my only option for cutting low frequencies from my main speakers and routing them to my sub. Doing this improves the sound of my main speakers - but I assume this varies from setup to setup.
Opinions differ regarding what is better if you able to choose. Also, some choose to run their speakers full range and blend the sub into the mix where the mains trail off.
There are many articles online about this subject, and again, opinions differ.
If you have the options, trying each and picking which you like best would be my advice.
Disclaimer- I'm far from the most knowledgeable on here.
Hope this helps,
gary