I know, when I got my TDI in 2000 I was close to getting the HX, I raced many VTEC type engines and I was very happy with them. The TDI can make about 180 WHP and be dependable. The torque is hard on the driveline but drivability ws great, better then any car I've owned before or after. I decided to pickup a HX to see what I missed out on. I built a unique two stage VTEC engine based on a D15B JDM head. The I toss a turbo on it. I run it on regular unleaded at 200 to 220 WHP. I could have built it for +100 WHP if I wanted to run expensive stuff. My Civic is much faster then my TDI even with the low HP turbo, IMO the Civic is a much better car and platform, except there is little in gear torque, I usually have to down shift two gears for any type of performance, and lag is not bad with my setup, but alas nothing like a VNT-17 and a diesel. This is partially offset by the Honda having the best shifting trans in the world. So while my TDI could give a scare to a V8 Mustang, it would lose in a longer type of race or be beaten bad in the 1/4 mile, the Civic will kill just about anythig this side of a well driven manual GT 3 valver.
So I'm at 43 MPG lifetime with my Civic with 25% more HP, 15% less weight, far better wishbone suspension, far better trans but um 1/2 the torque and that is what I uses 99.9% of the time.