Almost one year ago, I bought a Sapphire Radeon HD 4890 GDDR5 at www.tigerdirect.ca. As I was surfing on their site recently, I've seen the Radeon HD 5570 GDDR2 for only 100$. I asked myself if it was worth it to buy this new card, but I want to know what is the main difference on these different points:
GDDR2 vs GDDR5
Sapphire Vapor-X technology or not
5570 vs 4890
GDDR2 is significantly slower than GDDR5, but that might not even matter considering the 5570 is such a weak card. The 4890 will KILL the 5570 performance-wise. Sapphire vapor-x is just a nice cooler on the card made by one of the manufacturers. Vapor-x doesn't matter.
But really, the 4890 is an awesome card, don't even think about trading it for a 5570. The 5570 is less than half as powerful as a 4890, and DX11 really isn't very important, at least in the next few years.
The 5570 is a HTPC card. Not a high-end gaming card (even the 4890 is from the previous generation, it still has a nice reputation). If you're a gamer and you like to play definition games and are planning on buying crysis 2 the 4890 is the best choice between these 2. however there are other cards that could be better and could take advantage of crysis in DX11 ( HD5870 for example, or 5850)