Resolution, probably. (If you've seen my art, you know what I mean)
I understand how to deal with anti-aliasing now; it'd be feasible for me to finally get rid of the pixels. But am I gonna? Hell no. For one thing, it would make even simple editing 9000% harder, and my time is limited enough as it is.
Even without anti-aliasing, I could just make everything bigger...but I'm not gonna do that either. I like having small files that are ~130 KB for a full comic page. It's like a Great Depression-era sort of thing: I grew up with cheap computers with limited file space, and I've learned to like being able to conserve. Even now that terabytes are a thing, old habits die hard.