Question about A records vs NS records

[pdp76]

I have a domain registered to me, call it xyz.com. I wanted e-mail to [email protected] to goto a particular mail server, so I setup MX records on my domain registrar's DNS server to point to the mail server I use. However, I want all other type of traffic (non e-mail related) to goto my web hosting service which is on another server, and the web hosting service has their own DNS server which I can use as well. The obvious solution here is to setup an A record on my domain registrar's DNS server that points to the IP address of my web hosting server. However, since my web hosting service also provides me with a DNS server to use, would there be any advantage/disadvantage or problems if I setup NS records on my domain registrar's DNS server to point to my web hosting service's DNS server vs using the aformentioned A record method?

To spell it out

A record method:
xyz.com A xx.xx.xx.xx

vs.

NS record method:
www.xyz.com NS ns1.webhostingservice.com
www.xyz.com NS ns2.webhostingservice.com



Thanks in advance.