I'm posting page by page, because that's how I'm used to reading webcomics, and I feel more comfortable with it; when something is drawn page by page, it probably works better to read that way. Otherwise, it's easy to end up with a situation where the reader can't really tell where one page ends and another begins, because they're stacked on top of one another.
Also, when drawing page by page, you most likely compose your panels and such to be read a single page at the time. Unless you draw each page with a scrolling reading-method in mind, it might come off looking a bit weird.
Also, scrolling for long chunks of time bothers me, even on mobile devices, because I find it easy to lose my place - page-by-page, on the other hand, is easier for me to keep track of.