I much prefer webcomics. I don't have to wait for the whole thing, as I can read as updates happen with individual pages. There's a lot more communication between author and reader, and there's often a comment section in which readers can interact. The author gets that feedback, as well as pageview tools to help tailor the experience to the readers.
Of course, downsides being the author might not get paid as much. But if I'm seriously in love with a comic, I'll always buy at least some merchandise or a hard copy of the comic when I get the chance. I rarely pick up a comic that I've never read before, simply because it's a financial risk that isn't worth the possible gain, to be honest. As far as a marketing perspective goes, at least.
True, but just as buying a comic blind is a risk for me, marketing your comic is a financial risk to you, just on a grander scale. All financial gain is based on risk and time put in, factoring in marketing and demand of the product.
Of course, as a consumer and not a creator, my personal agenda as compared to the author's agenda are baseline differing. Which is where you get the idea of moderated consumption. In the web-based world we live in, there are too many webcomics out there for the idea of actual profit to be vaguely achievable. People would just move on to a less desirable but more available reproduction. Sorry, rambling. Marketing is just a really cool thing to think about. Constantly cycling, constantly redundant.
I prefer reading a comic online before buying the hard copy, and most likely wouldn't buy a comic unless I could read it online or in a bookstore first. After I've read it once I'm hard copy all the way!
I personally think that webcomics are an excellent way to launch your story out there, and gain an audience. It gets people hooked, and then when you eventually publish it and start selling hardcopies, you will have an easier time selling them.
That is strictly my own opinion, just based off of how I view webcomics. I am much more likely to buy a comic if I've read about it online. Main reason being, is because I already know it's good, and secondly, I admire the artist for putting it on the web, so I want to support them as much as I can.