I submit this for consideration.
If you want to move weight and aren't going to drag race the car the 700R4 has the better gearing beginning to end. Even if you are going to drag race it, the 700R4 is the way to go as from experience having built over 1000 of these units(mostly 4L60Es), and had them in everything from Impalas, GTOs and wheel pulling 10.5 sec. 440rwhp LS1 Camaros. The truth is that if the 2004R was the better transmission, then you could install a 2004R
E, but GM made that choice for you as they continued develop the 700R4/4L60E trans and install it in trucks, vans, caprices(b bodies), camaros(F bodies), and even the corvette. They wouldn't have done that if it was the lesser of the two transmissions.
I have enjoyed mine endlessly after installing back in 1996! Driving to the race track(4.10s), pulling a .4 sec better pass(13.4sec-1.8 60ft, 4100lbs 70 impala) than the same combo with the TH 350, then driving it home and then driving to work the next day, and the day after that and the day after.....
The truth is the only problem I had was the time I launched at the track and ripped the hub of the convertor turbine, from the turbine. Had the convertor fixed and was back out tearing it up again.
I've built Metric 200, 200-4Rs, 350s, 400s, 4L80Es, and 700R4. Metric 200s, has stamped sheetmetal drums and is a grenade. 2004R basically the same internally with the edition of an overdrive drum in front of it all. 350, great trans but has only three gears. 400, bulletproof, but it has only three gears. 4L80E the way to go with big horsepower and gears- needs controller and cost could be a deal breaker. The 700R4, not too hot, not too cold, not too hard, not too soft.........it's Juuuuuuussst right!!!! The best of all worlds- my opinion of course!