Found this opinion on this subject....
AMD Radeon 6790 Unseats Aging 5770
Dateline: 05-09-11
The near ancient Radeon HD 5770 finally takes a seat as AMD rolls out its replacement: the 6790. For about the last 9 months the 5770 has acted as the “cut-off” card for Fox Tek, that is, the card we use as a barrier to entry into our coveted graphics card lineup. We felt that at about $150 we separate the riffraff of pretend video cards from the entry level serious gaming cards.
nVidia did not have a suitable card back then to compete with the 5770, but they didn’t care as much as they dominated the high-end. Therefore, any gamer who thought they wanted to be serious about gaming but wasn’t sure was directed to the 5770 as our go-to “try this first” card. Fast forward to May 2011 and we have a new entry-level from nVidia to combat the AMD squatter: the GTX 550 Ti.
The 550 Ti generally beat out the 5770, but AMD then dropped the price of the 5770 by $20 to alleviate the string of nVidia’s new release. Now as a more permanent solution AMD released the 6790 at $150 to overtake the 550 Ti as the dominant card in the market in its tier.
Not surprisingly, it worked! AMD usually focuses on the low-to-midrange more than nVidia, so it's not startling when they do it right. (Side note: at this point in time AMD also holds the heavyweight champ title as well with the 6990, but it’s really just a coincidence that they have winners at most price tiers until nVidia gets it act together). The 6790 is $20 more than the 5770, and out performs it an average of 15%, justifying its price hike. This also means, against the 550 Ti, it is around 13% faster, but costs the same.
The tests were interesting though, in games like the Far Cry 2, Hawx 2 and Star Craft II, where the 550 Ti out-performed the 6790 by roughly 9%. If we remove those three games from the collective numbers, we get a result of the 6790 topping the 550 Ti by 30%. More simply the previously mentioned games are saving the 550 Ti from being outclassed by a little over 10% to just under a third vs. the 6790.
These numbers allow Fox Tek to ease the 5770 into retirement and place the 6790 guarding the gates of entry-level gaming. The Radeon 6850 and NVidia GTX 460 still sit comfortably out of reach for the rookie, but so do their price tags, making the 6790 a perfect fit into the AMD lineup.
http://www.foxteknology.com/index.php?option=com_content&view=article&id=128&Itemid=468