That comparison is poor, The best detailed review comparison between the two flagship single cards is here, with everything cranked up
http://www.xbitlabs.com/articles/video/display/quality_vs_quantity.html
You've only got to do a quick search over at overclockers to see there always the ATI v Nvidia fanboys in the same vain as the AMD v Intel fanboys too, so regardless of any reviews or facts, theres those who simply will dis the opposition
In nearly every test, in particular in OpenGL, The GX2 is ahead but not enough to warrant the extra money imho, The X1950XTX can be had for £287 inc vat from overclockers at the moment, the Nvidia cards do have a much much lower power consumption and heat though
The above test and the majority I've seen also have ATI winning the image quality debate, especially with high AA/AF settings, this is the case in nearly every review
I can't comment on SLI v Crossfire as I'm not clued up on it though
As for sub £200 cards, ATI wins hands down, The X1900XT 256Mb can be had for a ridiculous £165 inc vat, easily clocks to X1900XTX core & memory but is almost £80 cheaper (albeit the X1900XTX has 512Mb) In the vast majority of games and when not using say 1600x1200 res, theres not really much "noticeable" difference between this and the flagship X1950XTX, especially if you aren't running 16AF and all textures fully maxed out
Nvidia will however have the worlds first DX10 card with SM4