Wheelspin? On pavement? That's extremely rare. Most R/C tires, unless super hard, have plenty of traction to flip the car over, wheelie-style.

Regarding the .26 vs .20 argument, assuming both have the power to push the vehicle through the air (and drivetrain friction, rolling resistance, etc.) to their maximum rpm, it all comes down to that max rpm. If the 3.3 can do 35,000 rpm and the Picco .26 can pull the same, they'll hit the same top speed. Whichever revs higher will potentially be faster, displacement is not the only factor. You could drop a 400hp Chevy 350 in your Jato, in theory, and probably hit about 10mph for a top speed. No shortage of power, just a major shortage of rpm. A nicely-built, street-oriented 350 Chevy will rev to 6000 rpm, while an R/C engine will do 35,000 or so. Assuming the same gearing, the Chevy-powered vehicle will only be able to achieve about 1/6 the rpm of the R/C engine-powered vehicle.

So that's what it comes down to: gearing! If you can, gear the truck taller for the Picco, meaning a larger clutch bell and/or a smaller spur. My RC10GT could do about 35-38mph with an O.S. .12CV-R engine and probably less with the "sport" .21 I installed with the stock gearing. But I changed the bell/spur gearing from 16/66 to 18/47 and was able to exceed 60mph (clocked) with the .21. So more power is good....as long as you use it properly. My next project is to drop a Picco .28 into the GT with a 20 or 22-tooth bell and 47T spur and shoot for 70mph.

All that said, the Picco will have more power at nearly every point in the rpm range than the 3.3, so yes, it will arrive at the top speed faster.