ARE www-data and $USER folder permissions MUTUALLY EXCLUSIVE?

I have a joomla intance on UBUNTU, inside var/www/joomlafolder. My question is simple. If i tell my droplet to:

sudo chown -R www-data:www-data /var/www/joomlafolder 

then i gain ability to upload and write using the famous joomla administrator panel through my browser. But then i loose the ability to write via sftp, which i will re-gain if i order my my linux droplet to:

sudo chown -R $USER:$USER /var/www/joomlafolder 

But then again i will loose the abilities to write and upload through the joomla administrator

So my question is: CAN A USER HAVE BOTH THINGS AT THE SAME TIME? www-data persmissions and $USER:$USER (for sftp)??? Or are these two mutually exlusive?

Thanks in advanced