It has been established at Search Summit Conference that it is so excellent to use 301-redirect for the permanent move of a site to a new domain.
Adam Lasnik said this during the conference meeting that it is not good to use 302-redirect which is the temporarily move in the old pages i.e. if the page file names are not changed. If it is done then the pages will be re-indexed by Googlebot. He also suggested that to keep the old site alive till the new pages are cached.
Another idea was suggested by the support engineer that to include Xml sitemap in the new domain for the faster indexing. Where Adam assured that usage of 301-redirect with Google sitemap will surely make the relocation process fast without trouble and the also the entire site re-indexing much faster without using 302-redirect.