Power for the buck? I don't think there is a winner, at least from where you're at.
Swapping in the 5.0 drivetrain would be much, much, much easier since you have a complete donor car.
If you were to go the 4.6 route, after you actually built a complete motor (a couple thousand dollars at least), you would have to get everything else to swap it into the car - wiring harness, transmission, computer, ect. There is a few thousand you could have put into the 5.0.
I assume the roller car you have was a V6?
'94 Laser red 'vert. Still a 5-oh... for now