Comparison:
V8
price: $59 (newegg)
weight: 866g
number of heatpipes: 6 each side
fan RPM: 800 - 1800
612 PWM
price: $50 (newegg)
weight: 806g heat sink + 104g fan
number of heatpipes: 6 each side
fan RPM: 600 - 2000
I would pick 612 because it's cheaper, slightly heavier and has a wider PWM range.
EDIT: if you value quietness, also consider Scythe Mugen 3. Similar to 612 but the idle fan speed can be as low as 300 RPM.