In Lotus Web Content Management V7.0 you can use the JSR 286 Web Content Viewer Portlet (aka WCM rendering portlet) for rendering content that is hosted in the Web Content Management repository. You can also address the WCM rendering portlet via the Web Service for Remote Portlets (WSRP) standard and thus integrate the content hosted on a remote web content repository. See http://www-10.lotus.com/ldd/portalwiki.nsf/dx/Performing_remote_rendering_with_WSRP_and_the_JSR_286_web_content_viewer_lwcm7 for how to set this up and the limitations when doing remote rendering.
The default assumption should be that web content rendering is done locally. In most cases web content is an integral part of the web site, like the portal pages and therefore it does not make sense to have the web content remote. In most cases you also want to have the access control set consistently for the portal pages and the web content, which would require additional work in the remote case.
Lotus Web Content Management and WebSphere Portal 7.0 also allow you a tight integration between the portal pages and the content being rendered by mapping pages to WCM site areas and exposing the current selected content item as part of the friendly URL path. All those benefits would be lost when using remote rendering. It also will make it much harder to leverage site analytics features that would otherwise work out of the box for local rendering.
Another consideration to keep in mind is that the convergence between WCM and WebSphere Portal will continue in future releases and add additional features which likely will only be available in the locale rendering scenario.