Honda Civic ESi uses the D16 series engine, which is a
single-cam VTEC engine. Honda Civic VTi uses the B16 series engine,
which is a twin-cam VTEC engine. In terms of power, obviously the
VTi has a higher power rating than the ESI. However, if I am not
mistaken, the VTi is classified under the high performance car
category, which means insurance premium for the car will be much
higher than the ESi.
The B16 engine is also used in the EK Honda Civic SiR and
subsequently, the B16B engine in the EK9 Civic Type R. In short,
without the VTi, we won't have the Type R range of cars we know
today.