bear in mind @ 300mm on an APS-C DSLR a lens is going to be the equivalent of a 450mm lens on full frame, and most ballheads have a phenomenon known as lens droop,all ballheads do it to some extent and I have had so many issues with lens droop, Especially with my birding and macro work I got a Manfrotto 405 Geared tripod head, and now I have absolute precision of camera movement and no lens droop. However the 405 is a big tripod head, and it needs a decent pair of legs to support it, and the camera you are using.
My review of this tripod head can be found
Here
Manfrotto 405 with K10D w/Grip Sigma 100-300mm f/4 APO EX DG and Pentax AF540FGZ