Power 25 1250kv APC 10x7E tests for P-47 with stock collet and Dimension Engineering SportBEC.

3S with Exceed 60A Opto ESC and Zippy 2650 3S 30C

Full throttle
467 Watts
41.9 Amps

4S with Exceed 60A Opto ESC and SkyLipo 2200 4S 20C 40C Burst

Full Throttle
932 Watts
63.2 Amps

About 2/3 throttle
493 Watts
32.9 Amps

418 Watts
26.82 Amps

What's interesting is the 4S produces more watts with less amps than the 3S if you compare the 467 watts (3S) and 493 watts (4S) figures.
As long as one doesn't go full throttle with the 10x7 on 4S, it looks like a good prop to go with for 3S and 4S since the E-Flite Power 25 1250kv has these specs regarding amps:

Continuous Current: 50A
Maximum Burst Current: 58A (15 sec)

Edit 11/18/2011: Regarding this statement:

I now know the answer after listening to Lucien Miller on ATTF. Basically, if you increase the voltage by going from a 3S to 4S battery, you need less amps to generate a given watt number which is why you go to a higher voltage battery when you need to generate more watts.

Flew 4S for the first time on any plane tonight with the following setup for my P-47:

E-flite Power 25 1250kv (it turned out the 870kv I thought I had purchased with the P-47 was actually a 1250kv)
Exceed 60A OPTO Brushless Speed Controller ESC (w/o BEC)
Dimension Engineering SportBEC
APC 10x5E
SkyLipo 2200 4S 20C (40C burst)

And all I can say is WOW! The burst of power when I go full throttle took a few times to get used to. Along with the installed retracts and flaps, I added 14g of lead on the inside of the air flow exhaust to counteract any any extra weight up front.

I enjoyed a few flights with my Parkzone P-47 today using both 2650 and 2200 3s batteries. The power system is an E-flite Power 25 870kv, Thunderbird 54 ESC, a Dimension Engineering SportBec, and an APC 10x7 prop. Landings were very smooth with flaps, but the plane rolls for a long time so I have to make sure to touch down early. I'm interested in putting in a 4S capable ESC so that I can use my two 4s 2200 batteries, although the present performance is fine. What's amazing is how quiet the E-flite Power 25 is. Someone asked if I had a motor on on when I was cruising a medium speed with the plane.

Edit 8/22/2011. I opened up the cowl to switch out the esc, and lo and behold, it was actually an E-flite Power 25 1250kv although the person I purchased it from said it was a 870kv. Pleasant surprise to see the more speedy motor.