I don't know if we will need 256MB cards, or not, but the memory requirements of games are a lot more likely to go up rather than down. New motherboard / video card designs may make current video cards obsolete faster than increasing memory requirements, though.
Like all Radeon card makers, Sapphire starts with ATI's reference design, and may make minor changes (I don't think anyone makes major adjustments anymore). Part of the price difference is because ATI can charge more being a major name brand, part because the Sapphire card I bought did not have a software bundle (I don't really like the types of games included with video cards anyway).
As far as I know their video card quality is not any lower.
