Is this even a useful feature? When I turn it on in my router and they ask me what my speed is for upload and download...should I use the slower upload and download speed results I get from this site or should I use [this.site.has.been.blocked.for.spamming] or speakeasy which say my speed is faster? What is an optimal way to use this feature so nothing in my network takes up too much bandwidth? Thanks

 I use it for VOIP, this makes the VOIP router priority higher incase  there is heavy network traffic.

  I would use the advertised bandwidth.

Not at all unless you have a machine that you don't care what the usage is,and uses a lot, and will be limited when there is other network traffic.