AMD Radeon R9 270 's Advantages
Boost Clock has increased by 19% (925MHz vs 780MHz)
Larger VRAM bandwidth (179.2GB/s vs 64.00GB/s)
896 additional rendering cores
AMD Radeon R7 340 OEM 's Advantages
Released 1 years and 6 months late
Lower TDP (50W vs 150W)