Yeah the $35 vs $50, or the 411 horse vs 450 horsepower questions are pretty much what this thread is about (although I suspect the 3.5TT is going to have 450-500+ horsepower, not a paltry 411). Of course you're going to pick the bigger one.
If I was shopping a regular F150 I'd choose the turbo 6 everytime. I don't care about a lot of power for putting around town. But in a Raptor... of course you want more power.
I suppose if we had more info it could be a more telling poll, such as (and I'm just making up numbers here):
1) Standard V6 Turbo, 500 horsepower, 16 mpg, 600 lbs, OR
2) Option V8 Turbo, 550 horsepower, 12 mpg, 850 lbs, $4,995 added cost.
In that case I might save my pennies and go with the V6.