E-Fans
Both are good although you'll hear a lot from folks who simply don't understand .
An E-Fan run via a relay and wired live , is the way to go as it allows you to delete the stock fan & should , freeing up a few HP and reducing noise considerably .
Use the biggest fan that'll fit and no , pusher fans are NOT less efficient .
Plus , by wireing it live , it'll come on a few moments after you've parked & locked the truck on hot days or after a hard run and cool things down , reducing underhood " heat Soak ", this is a very good thing indeed .
I personally , like to re-core the stock radiator using the widest core that'll squeeze in (more rows of tubes) as this way , the thermostat does all the temperature coltrol work as it's supposed to , not having the marginal stock radiator mandated by GM's bean counters , be working overtime and barely keeping up .
That's my story , backed by years of real world experiance and I'm sticking with it .