Multisite advise- Subdomain Vs Subdirectory

Hello Guys,
I′building a multisite that I need to have the same template in many different languages.
Each language I need to be a completely different website and have the need to all of them be very visible in terms of major search engines.
I may in the future buy another domains to park under my main domain to give more visibility to websites in specific countries.
Been reading a lot about this and I′m very confused, I thing the opinios differ a lot.
Can you give me some good advise? shall I configure my multisite as subdomain or subdirectory? what is the most effective way to suit my needs?
Appreciate if someone can show me the way.
Regards