Why changed from turtle or dugong? 

I'm also having a City 2006 VTEC. Believe me when I said, in terms of torque and acceleration pickup, it can kill PE anytime, even with a LCP on. I seriously doubt the new City will have fc like PE unless your friend really heavy footed.

Low range torque wise, idsi a bit stronger BUT when hit mid-range and above, idsi will begin to struggle after 120km/h. That's where vtec excel when the 2nd rocker up moves...VTEC activated. Once activated, speed will goes up so smoothly and effortlessly to 140>160>180 very easily. 88hp vs 110....that is both with minimal torque loss due to CVT tranny and electric steering.

iDSI was discontinued later BECOZ although in closed environment testing, it saves FC better than VTEC but in real life, its actually not much difference in FC savings, a minor bit only. Overall performance especially at mid-high range  suffers a lot vs VTEC thus could not justify the miniscule FC savings over VTEC. Overall VTEC performance is much stronger overall be it low range (almost similar), mid range (almost similar too but VTEC pull ahead much easily when approaching higher speed).

That's when idsi consume fc like mad coz not enuf power to climb. VTEC will also makan minyak like mad once activated but the way it zoom up to 180km/h is so effortless its worth it if you're in a hurry.

The meter cluster of VTEC is a bit cartoonish but I like it a lot.....similar to sport meter vs the boring meter of idsi.

There is no definite answer.
For me wax evry 2 months, polish perhaps once in 1/2years