There are a few pro's and con's when considering Plaxaco, Linkedin, or personal web site as a professional network. Plaxaco and Linkedin have formats that are already established. A web page can be created and changed however the user sees fit.
Plaxaco seems to me to be a more businesslike Facebook. You can add RSS feeds and keep a calender. There is an option for an e-card. It was easy to navigate in Plaxaco. You can add and import contacts and join groups that share similar interests. Plaxaco seems casual compared to Linkedin.
Linkedin is very business-like in their presentation. It really focuses on networking and finding jobs. Linkedin is also easy to navigate, but a person is limited by what they can add to their profile. Although both Plaxaco and Linkedin have a wide scope of what can be added to a profile, there is a limit to what can be put in.
A personal web page is limitless in what a person would like to share. To be sure, the person would have to be very creative. That doesn't describe me. A personal web page is much more creative, but more likely to be less organized and user friendly. It is also harder to get people to view your site.