They aren't better than a "normal" backlink, a normal backlink would be considered a one-way backlink; meaning that only one site is linking to the other. A 3 way backlink, or correctly said as a 3 way link exchange is when two webmasters exchange links but with multiple sites.
yes, it works similar to one back link as well since you are getting a link from site A to your site B while you are sending link to Site C. Compared to one way back link is that you get all the juice while 3 ways linking, you distribute the PR to the third site. The good thing as compared to two way link exchange is that it may not look so reciprocal link in the eyes of search engine.
Nowadays, I don't think the tactic on using 3 way link exchanges has a lot of benefits attached to it compared to last time. Search engines like google can easily trace and identify 3 way so I don't think it makes any difference after all.
regular back links are better because they are one way, you will get the most pr juice from one way back links
This is very true but also hard to put together. The trick is to get as many one way relevant back links as possible. You can do this with articles and press releases. But I now use another service that automates the one way relevant links for me. I have put together a free SEO Guide that explains everything. Download it now if you want to. http://www.mcreasite.com/Free_SEO_Guide.pdf Good luck