I like both kinds of blogs. Some information is better consumed through reading and other posts are better understood through videos. I think it's up to the blogger to determine what's best at the time.
There are websites out there that are an extension, a web presence, of their brick and mortar store. They will have a short video of something they are selling accompanied by a short, 100 to 200 word, synopsis of that video. Their blog is both video and text.
Video is getting more popular and you can find that some of the time vlogs are reaching more people compared to blog. And with the blog it can be really good option but it can be subject to the copyright issues there. I have seen that blog works even to date. But the video is lot more popular and it can be used for many ways and reuse is definitely possible in such context.
Well, if you are a good speaker and you can show passion when vlogging and reach into peoples hearts / minds I would say it's a way better method to deal with. It's simple, it saves time for people if you are covering a big topic since they don't have to read it, especially if something is really complicated to understand. You can explain that over vlog much easier, be it by gestures, or whatever method, but in general, it makes life easier.
Videos are great for people who aren't shy, and, as @Makefort noted, have good speaking skills. In fact, videos are possibly more powerful than blogs because people are drawn toward television. In that case, someone good at videos has a huge advantage in the online business world.
Nonetheless, though, you shouldn't be down on yourself if videos aren't cut out for you. Plenty of people make thousands of dollars from blogs.
Simone, this is a tricky one. Most people are better with words than speaking, so a blog would be better for them. However, most people don't like to read these days and would prefer the easier action of watching a video.