Quoted from the link above:
Right. Let's not muck around. For straight power output, the V-TEC system craps all over the VVT system. The latest Honda V-TEC engine, as used in the S2000 sports car, makes 240hp odd out of only 2 litres - That's a sparkling 120hp per litre.
The V-TEC system is far more complex than the VVT, but it allows you to not only alter the cam timing, but to alter the valve duration and lift at well. It's really like having two engines in one - A 'sedate' one for grocery-getting, and the other a red-blooded high revving screamer.