Synology vs DIY NAS

Hi, Stumbled on this site and must say it looks great. Lots of info. I think this is something that I can do with some effort and maybe some support. My question what is the main benefit of me doing this. I am guessing for same money it is a faster system, so some value or cost savings. I am giving up anything in doing so…I am not up to speed to all the things that can be done however I can probably figure out how to have my systems back up and how to access it. What is the easiest way to force cell phones (photos to back up regularly). I kind of like the Synology system (some of the apps that it supports). If I go DIY and use the Synology software (which from what I understand is not 100% same as buying system)…what do I loose (I believe I need to monitor and maintain upgrades and some features do not work). Currently have WD Mycloud (its ok, does meet my needs). I wanted to set that as a off site back up and get a new set up for on site (home user). I am not power user so trying to determine if DIY is really going to get me that much more benefit. I do stream Plex, Use Sonos system, and my photo library and have two main computers which each have an spare drive internally that is backed up weekly to replicate in addition to my current backups on MyCloud which is just the core files that I am concerned with (photos/documents/downloads)

Any input appreciated.