Kv is RPM (in 1,000s) per volt, so all other things being equal, a motor with a higher Kv rating will try to spin the prop faster. In general, you can think of this like a higher gear in your car, a higher Kv is better for higher speeds. BUT you really need to look at the entire system in order to make any kind of assessment (Kv by itself is meaningless without knowing what battery voltage/current capacity and prop diameter/pitch).
Try playing around with some of the on-line calculators to get a sense of how the various components interact:
Webocalc:
http://flbeagle.rchomepage.com/softw..._imperial.html
eCalc:
http://www.ecalc.ch/motorcalc.php?ecalc&lang=en