Which is more powerful?

The motors power is in direct correlation to the batteries feeding it. If you are using good lipos then as stated above on 4s it will be comparable in top speed and out accelerate it every time. on 6s lipo the picco stands no chance what so ever, but the vehicle will be severely overpowered and a beast to drive and keep it going the way you want it to.

4s at a 125 amp draw will make 1850 watts (2.5 HP) and 4.06 ft-lbs. 125 is an average as it will peak up to 150+ when you peg it hard. A spike to 150 will make 2750 watts (3.7 HP) and 4.87 ft-lbs.

6s at a 125 amp draw will make 2750 watts (3.7 HP) and 4.06 ft-lbs. A spike to 150 will make 3300 watts (4.4 HP) and 4.87 ft-lbs.

the spikes to 150+ are just that, spikes. Average driving should pull 125 amps or under, but yes it is quite capable of handing that big block picco it's ass.

[othello]

Neu 1515 motors (castle 2200kv motor is based on this one) are rated at up to 2700W (for 30sek). While driving my truggy with agressive gearing and 10s A123 i measured short bursts between 2200-2700W. This is the power In ... Assuming an overall system efficiency of 75% which translates to 2KW or 2,72 HP power out of my system.

Typical .21 to .32 nitro motors hardly ever reach 2hp if you look at dyno graphs: ebmods, Nitrodynesystems or abmods.

Depending on the batteries you use i would say that you can get more power out of a Castle 2200kv when compared to a good .28. Due to instant torque from 0rpm on it feels even more powerfull.