I'm going to treat this as a journal entry for me, so only read it if you have the patience.
People who play covers and people who play originals are very different from each other. Some play both, but IME there's always been a priority and that's what defines them. I play both, but I grew up writing my own music and knowing that for me there's nothing quite like the rush of having a big crowd cheering you on because they like the music YOU'VE created. It feels a lot more genuine. I live for it. I've played in cover bands that suck bigtime yet play in front of hundreds of drunken college kids literally hanging from the light fixtures (got blackisted for it). It just however doesn't compare. If your originals suck there's a real slim chance you're going to draw any crowd that isn't more than just your friends and family.
I currently play in 5 different bands with roughly 20 different musicians, and do some subbing. I've played in countless original and countless cover bands. I get along with everyone, yet only get close to and really relate to the people who's priority is original music. That's not a judgement on the others, we're just from different worlds. I was going to write a whole list of differences but I think it pretty much boils down to this:
For me and the others who make original stuff a priority - music is also THE priority. It often comes before family, pretty much always comes before everything else. Dayjobs, girlfriends, cars, rent... . People who do the cover thing more often than not put priority on their day jobs, and live a little bit less on the edge. I'm pretty sure every cover band dude I know has a pension plan and health insurance.
All that being said, I love playing covers and clearly see the benefits. If anything, I pay a price for my NEED to do the orginal thing.
Covers pay. Covers open me up to lots of different styles. Covers introduces me to lots of new musicians, introduces challenges (doing a 1st time show with a band of people I never even met), gives me never ending opportunities to hone my performance and craft, allows me to play weekly in front of crowds of hundreds of appreciating people, strokes my ego, makes me lots of new friends... how could I knock it???
Doing originals is the only thing however that can satisfy the something in me that goes a lot deeper. I wish I could put my finger on it, but I can't. Sometimes it's a blessing, sometimes it's a curse. I think it's a common bond I share with the ones I get close to. I think it might very well be that thing that makes for the seperation of the 2 types.