Based on the specs you posted I would say the 4670 is likely to be faster then the 5550.
unfortunately specs doesn't always translate into performance, also they use similar but different architecture so it is hard to just compare them specs by specs.
as far as i know the 5xxx series uses a tweaked and improved 4xxxx architecture
that's why i need a hard evidence(benchmarks, reviews, etc) comparing the two and see which is faster, and how much faster it is
i have another question
how much slower a Radeon HD 4650 GDDR2 512MB than both 5550 DDR3 and 4670 DDR3?
Radoen HD 4650
Core Clock: 600MHz
Memory Size: 512MB
Memory Interface: 128-bit
Memory Type: GDDR2
Effective Memory Clock: 800 MHz Effective
Stream Processors: 320 Stream Processing Units
Texture mapping unit: 32
Render output unit: 8