I would say they are both of equal importance,
While FEEL is important, so are fills.
However, like you said yourself, feel and groove are king.
Fills can make songs memorable, but 98% of the time, it's the groove that you remember.
I like the way you can make a drum track contrast with everything else that is going on during a song.
Lasr Ulrich, one of my idols, taught me the importance of feel, while people like Alex Lopez, Joey Jordison and Mike Portnoy taught me the importance of fills.
Feel can only ever make a song get better,
Fills however, can make OR break a song,
That's just my opinion though