PageRank and Alexa Rank
 

Some sites have high PR, like PR4 but has an Alexa Rank of 8 million.
Some has 0PR but has an Alexa Rank of lower than 200k.

Is PR better to consider than Alexa rank?

Which brings more traffic per se?

I never look at PR. It's outdated now. I tend to go more off the Alexa rank but also take that with a pinch of salt.

both pr and alexa can be faked ...

You can have 10 hits/day and high pr rank. I do not really care about it.
Page Rank shows authority of a webpage in Google.
And Alexa rank denotes global traffic rank of a webpage.

thus making both worthless metrics.

You can reach alexa #10k or better easily with few $1000's worth of popunder across a month. There will be no any extra sale, but your alexa rank will look cool, and "how much your domain is worth" will be lots higher too :)