At the moment, I doubt you could say ATI is winning given that nVidia's 8800 series are out and seem to be dominating the benchmarks if you look at Tom's Hardware for example.
From the first link:
"On the signaling front, the new GDDR4 protocol now expand the chip I/O buffer up to 8-bit per two cycles, allowing for greater sustained bandwidth during the burst transmission, but at expense of significantly increased CAS latency(CL), determined mainly by the double reduced count of the address/command pins and half-clocked DRAM cells, compared to GDDR3. The amount of addressing pins was reduced to half of GDDR3 core, and were used for power and ground, which also increases latency.
Another advantage of GDDR4 is power efficiency: running at 2.4 Gbit/s it uses 45% less power when compared to GDDR3 chips running at 2.0 Gbit/s."