What does a NETCONF reply for a router's OSPF configuration look like compared with the CLI?

It contains the same OSPF configuration as the CLI, but structured as nested XML elements following the device's YANG model, inside an <rpc-reply>.

On an IOS XE router, the CLI shows:

router ospf 100
 redistribute connected subnets
 network 10.10.0.0 0.0.255.255 area 0

Through NETCONF the same configuration comes back as:

<rpc-reply message-id="…" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <data>
    <native xmlns="http://cisco.com/ns/yang/ned/ios">
      <router><ospf>
        <id>100</id>
        <redistribute><connected><redist-options><subnets/></redist-options></connected></redistribute>
        <network><ip>10.10.0.0</ip><mask>0.0.255.255</mask><area>0</area></network>
      </ospf></router>
    </native>
  </data>
</rpc-reply>

It is the same information, but now every value has a name and a place in a tree, so a program can read area directly instead of parsing a text line.

Requests use the same structure. For example, a <save-config> RPC from Cisco's cisco-ia model saves the running configuration, like copy run start on the CLI.