Hi Marcel,
Let us not forget that in order to be able to rank with your website, you will have to give the possibilities for Search Engines to make 3 steps: 1. Crawl 2. Index 3. Rank
One of the best solutions that I have seen for your case is what Specialized Bikes uses (www.specialized.com
So As I have seen they have an IP sniffing on the main address only: www.specialized.com which will then redirect you to your location's store (for me it is http://www.specialized.com/ro/en/home/ for a person from the US it should be http://www.specialized.com/us/en/home/ and so on for each country which they have specified).
This is good, because then in Google Webmasters Tools they can create separate profiles for each folder: /ro/ /us/ /fr/ etc.
This means that they can still create a sitemap.xml for each of the "stores" and they can submit the sitemaps from Google Webmaster's Tools and avoid crawling issues. (And if you check via proxy different local Google results, you will see that they still rank quite good).
The problem comes with the same language content on different countries where you could:
- insert Hreflang
- get local some nice LOCAL links for both
(at least this is what I would try to do)
Now to respond your question, I quote:
1- which redirect should we use? 301, 302?
A: This wont be a temporary redirect, so be sure to use 301! 302 redirect will retain the "link juice" on the old version. For reference check the following article of Dr. Pete: http://moz.com/learn/seo/http-status-codes
If we choose 301, then which version of the site will get the link juice? (i.e, /ca-en or /us-en?)
A: Depends who do you redirect to.
P.S. As you mentioned you will have duplicate content issue because of us-en and ca-en, which Ideally it shouldn't be a problem:
“Duplicate content and international sites
_Websites that provide content for different regions and in different languages sometimes create content that is the same or similar but available on different URLs. This is generally not a problem as long as the content is for different users in different countries.” _Source: https://support.google.com/webmasters/answer/182192
if we choose 302, then will the link juice remain in the original links? is it healthy to use 302 for long term redirections?
I wouldn't advise you to do so. If it is a permanent redirection, let it be a 301.
So before making the huge step, I would advise you to go through some steps:
- create a full list of incoming links
- Sort your list of links for relevance, quality and geo-location
- Make the change in the URL system
- Start contacting your most important linking partners and kindly ask them to change the old links into the new versions (from example.com to example.com/us/en/ or if it is a French link from Canada then from current version to the example.com/ca/fr/ version and so on)
I know it is really a huge work, but it will grow its fruits.
Good luck!
Istvan