Hi,
I'm not an expert in SEO, but SEO is mostly about trying to understand the search engines algorithms by analyzing results of different approaches.
Now, from my observations, here is how Google reacts with LE:
- Google will index content of the localized home page of the default portal language as the root of the site. If your site has french as default portal language and your french home page is /fr/accueil.aspx, the content of this page is what is going to be indexed for / by Google. Google probably doesn't send any language header when indexing. LE will not be able to detect user preferred language when being indexed by Google and will redirect to the home page of the default portal language. Google will follow the redirect and assume this is the content for /
- Other root language page will be indexed as their respective URLs. For instance, the english home page is going to be indexed for /en/Home.aspx
I personally believe this is a better indexing result that having a landing page for the user to select his preferred language. Google gives more importance to the home page of a website than other pages inside the website. If you have a landing page containing a link to the french and a link to the english home page, then this landing page's content is what is going to have more value to Google. I'd rather have the content of the default portal language indexed than the landing's page content.
You can try searching for "Adequation Informatique" in Google to see Google's indexing when using LE. I have tried in various country specific version of Google and all results are as I have explained.
The same logic seems to apply to Bing.
In any case, it is also possible to have a landing page with LE, by pointing the home page of every language to a landing page at the same level than root language pages.