The two browser method refers to the ability to get 2 cards that would otherwise make you ineligible for the second one, such as this blog post from 2011, for an opportunity that worked until January 2013 http://millionmilesecrets.com/2011/1...vantage-50000/

The pros were that you might save a pull while getting twice as many miles as you could without it.

The cons are that it doesn't work anymore.

There is a chance that you may have saved a pull by getting 2 Chase personal cards on the same day.