Question on sip registration
 

What is the difference between having voxalot register with my VSP to receive calls or...

Having my VSP forward calls to my user@voxalot.com SIP number.

Is there a difference in call quality when receiving a call?

No, there is no difference in call quality in both cases.
In some way is better to directed your DID to your Voxalot SIP URL than relying on SIP registration of Voxalot on your VSP account. Among other reasons, is more probable having a SIP registration failure that a SIP URL redirection failure, namely when your SIP URL destination has fixed IP address.
Regards,

Obrigado Carlos

New and confused
 

If I get a VSP like voipo.com to make and receive phone calls, and they also give a SIP number, what benefits exist to also use voxalot with the VSP? What am I missing here? Thanks. If the VSP offers everything then that should be enough.