System wise are they not the same? I know Pinguy has add-ons but works just like Ubuntu under the hood.
Not much, PinguyOS is based on Ubuntu, works with mostly Ubuntu packages and should almost be identical as Ubuntu under the hood. But it is not developed or supported by Ubuntu.
The main differences between PinguyOS and Ubuntu are
In the end, other than licenses and personal packages choice, some visual tweaks and scripts, it is not different from Ubuntu.
But since Ask Ubuntu only deals with official Ubuntu or Ubuntu flavors PinguyOS is off topic for most questions here.