My laptop diagnostic shows several pre-fails and has other issues so I am urgently shopping for a new laptop, my second using Ubuntu. I need a laptop with good graphics capabilities and have come across a couple with the Nvidia GeForce 840M graphics card. In other words, I do not have a problem now and am hoping to avoid one.

My research shows that there have been some bugs with Ubuntu 14.04 and Nvidia drivers (not just for the 840M driver) but that by a couple of months ago fixes were made. But I have seen nothing definitive, e.g. the Ubuntu Certification for laptops is barely starting with 14.04.

I am about to spend a 900 dollars and would love a little more assurance before I proceed -- my understanding is that a Live CD cannot perform a full simulation. Are there easy-to-recognize concrete factors which make compatablity predictable, such as specific models of computer and their processors?

I am a considering both a MSI GP60 with an Intel i5 4200M and an ASUS n56jn-mb71 with an Intel i7 4700HQ. Both are 64-bit and use a Nvidia 840M graphics card.