If you are looking for the best performance I would recommend this one:
http://www.exmodelengines.com/produc...cat=257&page=1
A 6x3 is a good all around flying prop, especially for sport type applications.
Perhaps the most important thing you can do to maximize performance is properly balance the propeller, no matter what size or type. An unbalanced prop will cause a serious decrease in performance. This is a pretty good tutorial:
http://www.youtube.com/watch?v=N02NHYrpA0g
Regards, Matt