Unfortunately the Dell replacement boards on that second one will continue to go out in my experience. The warranty replacements are refurbished parts that Dell sends out that supposedly do not have the NVIDIA GPU issue when in fact they actually do (source: My time working at Dell doing support for the business models). To be fair Dell was not the only system vendor affected by the issue but if you are interested you can read more about it here:http://www.tomshardware.com/news/gpu-failure-g84-g86-settlement,11400.html
IMHO I would seriously consider saving some cash once the warranty is out and upgrading to the E series latitudes if you still want a Dell. They had much fewer issues.