If you want to vote on Environment, Which is what I primarially do, you want to definetley vote Kerry.
Cobb would be much
better for the environment, but Cobb isn't going to be president, and Bush is the absolute worst President in a very long time to our environmental health.
What Clinton did... well, he was never anything anyone would call an environmentalist. Clinton was straddling the right edge of moderate during the 90's. Just as likely to be a foe of environmentalists as an allie.
Kerry on the other hand:
Has been
endorsed by the league of conservation voters. They have NEVER endorsed a presidential candidate in their 30 years but have this time. Kerry. Kerry has a 96% lifetime Environmental voting record with the LCV.
Kerry is one of the original Earth Day organizers.
led the fight against drilling in the Arctic National Wildlife Refuge
Kerry has sponsored legislation to increase fuel-efficiency and develop alternative fuels, opposed Bush's weakening of the CAA through changes in the New Source Review, voted to limit subsidies to logging in national forests, supported the roadless rule for national forests, is against mountaintop removal mining, he also sponsored legislation to incorporate environmental protection into trade negotiations.
Kerry also opposed the nomination of Interior Secretary Gale Norton.
You can get the LCV profile for both men
Here