Never go with a pusher. They don't work unless you've got the time and money to engineer something.
Fans from a parts house suck. No further investigation necessary.
if you're going electric, plan on a 50 amp startup draw and 30 amp running draw. If you're not going to run somethign taht heavy and have the charging system to support it, stick with mechanical.
Some of us enjoy the benefits of an electric fan such as on demand cooling with the engine off and no whirring finger chopping instrument of death under the hood.