Hi, these two tools are not used for the same things so choosing between them is not the question.
s4pe is used to edit and create the package files, and the contents therein. Even though you might not need it right now you should download it anyway as you will need it sometime in the future, it is a must have tool when creating or modding sims.
It can be found here:
http://sims4group.github.io/
Sims4Studio is a tool that allows you to create custom content, you can find tutorials on how to use it on their site. I haven't used it myself but I think it does what you want.
It can be found here:
http://sims-studio.proboards.com/