Fuck, its not that easy to say which is better.
SE traffic got the HIGHEST QUALITY - means great sign ups
But its very hard to get SE traffic. On the othe hand, you can get about 300.000 unique visitors from TGPs but they are not worth much.
Anyways, SE is the best if you get lots of it.
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Easy $$$ For Webmasters - program sell like crazy on all kinds traffic!