Females can be a bit aggressive around other females... just saying.
I have owned and run 7 Brittanys since I turned 18. M, F, F, F, F, M, M
I really cannot say one sex is easier or more difficult to train or better overall in the field ... my two males I own now do not roam whatsoever ... my last Female (turns 16 in two days) ... she was a big-time roamer ... would bolt from our front yard if given the chance from 1-4 years of age and then turned to be a homer for no apparent reason around 5 years of age. In the field she ran big, but she listened extremely well and never got too far out or lost.
All have been pretty darn good bird dogs and nice house/family dogs. My male that turned 10 a week or two ago had an absolutely phenomenal season that just wrapped up.
My fourth dog (a female) was probably my best all-around hunting dog ... pointing running birds at 10 months, retrieving waterfowl, etc.. She came from one of the best Brittany bird dogs of all time ... then again, when she was with me when I was in my hunting prime ... days hunted, plenty of vacation days allowed, younger and better shape, multiple species in a single day, go-go-go ... etc....
I ramble on ...