Short answer is I don't know. Guess I haven't been with enough to compare!But my two cents is - its all about motivation and practice.
If you like it, want to do it more, and actually be good at it- (give your partner pleasure), than you will become an expert.
I think that motivation applies equally to men and women alike.
I can imagine shemales being more into sucking cock, since even though they are feminine, they still have that strong male sex drive/desire thing we all have and maybe less hangups about performing oral sex. And of course they are more familiar with the equipment and what feels good to them.
That being said, the best blowjobs (and deep throat) I have ever had have all been from my wife (gg) who was incredible.
The best blow job/deep throat scene I ever saw was also a gg with Peter North. (lost the clip!
) She was an older, slightly more mature woman, and gave the best head I've ever seen on screen. Really made love to his whole body while she sucked him every which way for about 20 minutes! Needless to say, it drove him crazy.