Speed really depends on voltage, not capacity (mh). A 2400 pack has longer run times than a 1700 pack. Real ex*****ve race packs may provide slightly more voltage (above 7.2v with a full charge) which is why they often go a bit faster.

The difference in speed between a fully charged Radio Shack 1700 and 2400 would most likely be negligable. The run time would vary though.