VVT-I is an intelligent variable valve timing system adopted by Toyota.
CVVT continuously variable valve timing continuously variable valve timing mechanism
CVVT and VVT-I just have different names. For example, BMW is called Vanos.
The difference is that i-VTEC can change both the valve opening time and the valve opening time, while VVT-I or CVVT can only change the valve opening time.
Theoretically, i-VTEC is definitely better, but the complexity of the mechanism will increase the number of fault points, so the quality can only be compared by the stability of their respective systems.