Or if the helicopter tour is too pricey, Wings Over Kauai does a fixed wing tour for less money and flies pretty much the same route.

I was wondering what the difference is in experience between the helicopter and small plane ride? Why would one be better than the other?

Short answers, a small plane flies and a helicopter hovers

"...and a helicopter hovers"

Which means a helicopter can get to, and land in places an airplane can't, the base of a waterfall, for example.

Okay, but for the most part, the views from the air would be exactly the same then...

The helicopter gives a much bigger vantage point because the whole front is glass. Plus it can go very close to waterfalls and valleys and canyons. You feel like a bird in a helicopter.

There is only one helicopter I am aware of that makes a waterfall landing, not sure if it is worth the extra money for 30 minutes and a turkey sandwich.

Thanks all - I'm going to look into both!

Just as one can get seasick on a boat, one can get airsick in a helicopter. When we did a helicopter ride on Kauai, the pilot said he would make the ride as calm as he could, i.e. no fancy flying through valleys and canyons. Even so, you can get bumped around by air currents and that was enough to make me nauseous during portions of our flight.