AMD Radeon R9 280 's Advantages
More VRAM (3GB vs 2GB)
Larger VRAM bandwidth (240.0GB/s vs 56.00GB/s)
1280 additional rendering cores
AMD Radeon 550 's Advantages
Released 3 years and 1 months late
Boost Clock has increased by 27% (1183MHz vs 933MHz)
Lower TDP (50W vs 200W)