The best program to use for comics is the one you're able to use without thinking.
I do my comics partially or entirely in Illustrator. Sometimes I like to draw my roughs on paper and take that into AI, sometimes I draw directly into AI. I do this because I've been using AI as my main medium for a decade, and I really never have to think about how to operate the program any more.
I find a combination of Photoshop and Illustrator to be the best for me, although I wouldn't mind playing around with Manga Studio. Panels aren't THAT hard to do via selections, but if I need a more complex shape then Illustrator does the trick. Plus it's great for word balloons.
I find that most beginner comic artists overdo funky panel shapes anyway, so it's nice to have those be a little bit more difficult. Then you have to sit there and think "do I REALLY need this panel to have seven corners? What are my readers going to get out of that?"
Hah, yeah, you're right on the seven corners thing. I'm honestly not entirely sure what I meant by unconventional panel shapes because I tend to stick to varying sizes of squares and circles. After I made this post I realized my problem is probably mostly due to not being very comfortable Photoshop's tools beyond brushes, so I'll have to practice more and see if I can get the hang of it.