I am looking to install a new social bookmarking site but i want to know which is best script either pligg or phpdug
and i also want to know phpdug whether is do follow or not?

yeah but pligg support is very bad and even templates doesnt meet what others are looking
and i already had one pligg site anyway i will use pligg since they more mods than phpdug but sappming is easy to spammers
the only main reason is their code can be used to spam without commiing to our sites to add

I've used Pligg before and actually found it very good. If you get the site setup properly, and get someone to code you a nice template, it can look very good.