NVIDIA Quadro K5100M 's Advantages
More VRAM (8GB vs 2GB)
Larger VRAM bandwidth (115.2GB/s vs 32.06GB/s)
1280 additional rendering cores
NVIDIA Quadro P400 's Advantages
Released 3 years and 7 months late
Boost Clock has increased by 62% (1252MHz vs 771MHz)
Lower TDP (30W vs 100W)