As a person making a comic, the vertical scroll adds lots of great things while taking away some things too.
Pros:
1: You can control the narrative better when scrolling. There is very little chance of the reader looking forward or down so you don't have to worry about reveals. You control when the reader sees something.
2: Long dropping panels are available to show someone falling or the like.
Cons:
1: No splash pages. The format doesn't allow it and specially at 900 px across.
2: Most panels have to be square or tall. With the limitation of the 900px across, wide panels just become small panels. It's hard to show action in the horizonal plane. So the trade off is tall for wide.
I would say as a reader, I don't mind either if done well. Scrolling comics tend to be slide shows, where you see lots of dialogue and a picture every once in a while. You can't get away with that in a normal formatted comics. The inverse is normal format comics with lots of portfolio style pieces with dialogue telling me what's going on.