Hey Wayne,

maybe the emissions rankings do depend more on the MY and market, but for example in the Australian market I found these rankings for Prius vs HCH:
Greenhous Ratings (GR) and Air Pollution Ratings (APR) 1-10 with 10 = best
Prius GR 8.5 APR 9
HCH (CVT) GR 8 APR 5

On the US EPA website you can find these ratings:
Greenhouse Gas production in tons/yr (GP), and Air Pollution Score in lbs smog / 15k miles (APS):
Strangely, the EPA site still does list different values for CA vs rest of US on all of these cars (Prius and HCH), it also lists two very divergent sets of results for the HCH, I don't know why, maybe Honda made some substantial improvements through the MY. Below I list the CA values as the best ones.


Prius GG 3.5 APS 9
Insight GG 3.5 APS 3
HCH GG 4.1 APS9
HCH second listing for CA GG 4.1 APS 3
Accord non-hy GG 6.5-8 APS 6-9 depending on location and engine.
Accord hybrid GG 6.0 APS 7.
This latter comparison is interesting in that the hybrid version of the Accord has lower GG values, but higher air pollution than the least polluting non-hy version (4 cyl).

So, within the resolution of these ratings in terms of air pollution score, Prius, HCH in one of two versions, and one of the Accord non-hybrids achieve the rating of 9.
Of all the cars, the Prius has the best combined score of GG and APS.
While this of course is just a coarse set of measurements with results given in different ranges, and subject to the way these tests are performed, I do think one interesting thing to note is that the Prius is consistently ranked as the car with the best cobined score, by all agencies where these cars have been tested (US, Europe, Australia), under different criteria, and all these agencies have labeled the Prius as the 'greenest' car. Some admittedly include additional criteria in their labeling, based on the amount of energy involved in manufacturing, amount of recyclables used, etc... Personally I think when all air pollution measures are considered, it's virtually impossible to distinguish the most recent crop of cars in terms of polluting emissions (Prius, HCH, Accord), which I think is a great acchievement!
I think once again the bottom line is that all these cars are great, and anyone who chooses one of these cars over other, more polluting cars, is doing a great job! Of course, how much our individual cars will spwe out will depend a lot on driving style, location, season, etc.. Another thing I constantly force myself to remember, is that even though I drive a Prius, I may end up polluting much more than someone who drives a large SUV, if they only drive 1/5th the distance I do, per year...
M