I've read a lot of reviews and threads comparing these cards. It seems to be nine tenths of the topics in this section of the forum. Most of the questions don't really help me much.

I like to game a little. I'm quite happy booting into Windows to do that though. So my question isn't something like 'what card is better in wine?'

I prefer to use Ubuntu for everything but the times when I occasionally game (or am using QSC Creator at work). I particularly like to use the dvi/hdmi/vga/display port (dvi right now, but I am looking for a new laptop) and plug it into my HD tv at home, to watch video.

On my outdated laptop with an ati card (HD2300) this is impossible with linux. I'm resigned to that, and don't care about potential solutions, because I want a new laptop anyway. There are some decent laptops with NVidia cards, but there are a couple with ATI cards that really appeal.

So now for the question (i.e. sorry about the drivel above, here is the tl;dr):

With a HD5xx0 card (5770 most likely) and Ubuntu, what are my chances of playing HD video to a plasma/projector via HDMI/display port? Better or worse than with NVidia? If worse, how much worse? I'm perhaps an intermediate user of Ubuntu.