This extremely useful article shows the advantages and disadvantages of various possibilities to structure a website. While going for a different domain (e.g. domain.fr instead of domain.com) to easily geo target for a foreign market might be a great advantage, no authority or trust is being passed by the domain that already exists, which obviously is a huge disadvantage. Like always, first of all you should focus on your goals – what do you want to achieve now, where do you want to be in five years? A clear and constant website architecture is a make or break for SEO, so I really recommend you to read the whole article, which also has a very clear short summary at the end http://www.webseoanalytics.com/blog/multiple-domains-vs-subdomains-vs-folders-in-seo/
How to properly rename a domain
You want to change a domain name from example.com to anotherexample.com and wonder which is the best way to do that from a SEO point of view? First of all, use a HTTP status code 301 redirect to redirect all your old pages (that means every single one!) permanently to the new ones. After that, check both external as well as internal links to pages on your site and be sure they point to the new domain name. Plus, create and submit (Google Webmaster Tools also helps here!) a sitemap.xml of your site. More on that here: http://webmasters.stackexchange.com/questions/3399/renaming-a-domain-and-preserving-pagerank