I have a question about the domain that I have now. It's PR3 but I don't like it anymore and plan on having a new website with a brand new domain. So , should I rather Redirect the PR3 Domain to the new site, or should I have it as a Parked domain?
I would suggest you use it instead. Put up a simple article about what people are looking for at this domain. Add some adsense ads and link from it to your other sites. That way it can make you some money and the PR would not be lost.
If its a PR3 then it has some valuable links. I would use the 301 Redirect so that your new site and domain can hit the ground running with some links.
So which way is better between Redirect 301 and Having an index with an Article, since I want Google and other SE to index my pages.
The 301 is better for your situation. Billion's idea is good if you weren't building a new site and wanted a couple of bucks from the domain while it lay dormant