K20 engine has more character with the vtec, however isf isn't too bad either, especially with some mods to make the engine come alive with burbles and the occasional pop. Secondary intake flap opens at 4k revs so is kind of like vtec in regards to sound. I guess it depends what you are after really. The isf makes a really good daily driver, that is comfy enough with 4 doors to transport the family around. It is fun to drive but does lack a manual gearbox. What I like is that I don't get much attention from others on the road, particularly from lads in fiestas giving you the thumbs up or trying to race you.
On the other hand, a Honda fd2 is in the similar price range, would be more engaging and cheaper to run. However it is a bit too harsh to drive the family around in.