Again, I agree that the comparison is between apples and oranges. The high-end GeForce GTX 2xx series GPUs, being older designs, still use GDDR3 memory while the newer Radeon HD 5xxx series at the upper end use GDDR5 memory.
Of course, price does not always matter. Just being astronomically expensive does not guarantee good performance. In fact, the most expensive GPU can actually be slower than an upper-midrange GPU for everyday applications.
And the HD 5xxx series are (abnormally) slow at 2D apps, such as Windows itself and 2D productivity apps, because of a bug in most of the existing driver versions for that series of GPUs. Until AMD officially patches this, I would not recommend any of that series of GPUs for all-around use.