Which is better?
 

I am currently building a formula 1 3racing f113 and I need it to have a high top end speed. I am currently looking at either the castle 1406 7700kv with a 5200mah 2s 7.2v 30c battery, or I am looking at a castle 1406 5700kv motor with a 5000mah 11.1v 3s 30c. Which is better?

Don't know?? Both sound very overkill for such a small rc car. They might be good fir speed runs on a super smooth road??

are u planing to run it on a track??

The 5700kv on 3s will have more power by virtue of the higher voltage. More power means it will pull higher gearing. Have you done any gearing calculations? I ended up with a 1/12 pan car and even with the highest gearing that would fit it took insane rpm to make it go fast. If speed runs are your goal you may end up with the 7700kv on 3s to get the rpm needed. There are other motors available with kv in the 9000 range as well.

Btw the pan car I had was a real handful at high speed. Getting there wasn't easy either, the power just made it want to spin out. I bought out someone's collection and just used parts that came with it. I believe it was a 9 turn brushed motor that I ran on 7s NiMh and geared to the max it was still only around 45mph bouncing all over my fairly smooth street.

if your goal is purely speed, i'd go 4000kv on 3s. that setup is capable of theoretical speed beyond 100mph quite easily. here is something to consider though, will a 3s, or even a 2s, fit? pan cars typically run 1s and as far as i know only a few can fit a 2s. you wont be able to fit a 3s in the stock battery location. i know you are building an f1 car, but they have very similar specs from what i have seen.