hey my friend wants a fantom engine. its gotta be slide and pullstart.

so whihc one would be better.... .12 or .15? he wants backyard bashing but also wants to control it

both engines reach essentially the same rpm, and since top speed is a question of gearing and rpm, they will both reach the same top speeds (since they are fantoms, they probably have the power in both cases). Typically the .15 will have a bit more power, so you get better low-end grunt, and it will accelerate more quickly. If he is ONLY interested in bashing, and NOT racing, go with the .15

I second that opinion.

whats the cheapest place to get the .15 from?

Probably stormerhobbies.com