When do I use "Uses" and when "are using"?

For example:

> 
> Computers uses RAM which is faster than disk storage.
> 
> 
> 

Or

> 
> Computers are using RAM which is faster than disk storage.
> 
> 
> 

The last one sounds more natural to me as a non-native English speaker, but I also see often "uses".

When do I use which?