The only condition that white Boxers are proven to be more prone to is deafness, which is due to a lack of pigmentation in the inner ear. They are also more prone to sunburn, but I wouldn't consider that a "condition"
During the war, Boxers were used as war dogs. A white coat (and even a lot of white markings) was unacceptable (too visible at night), and since meat was rationed breeders needed to spend their efforts on the dogs that would be useful as war dog. I'd imagine they were culled from litters at birth, although I can't say I've read that anywhere. The goal was to eliminate the white coat color from the breed (which proved to be impossible since white is not a coat color, but a marking pattern.)
After the war, the stigma surrounding whites continued, and in the US the American Boxer Club Breeder's Code of Ethics forbid the sale, registration, or *placement* of white Boxers. Breeders had to choose to either cull whites at birth, or keep them all. (There are those who took them to the vets to be euthanized, and let the vets find them homes.)
Happily, the COE was changed in 1985(?) so that placements of white Boxers was allowed. (They still cannot be "sold" or registered, although that will change at some point in the future.) There are still a few old-time breeders who cull their whites, but they are getting older, and fewer. Most breeders today place their whites in loving homes on spay/neuter contracts, and they often go on to be successful in performance events. Somewhere on the board there is a statistic about the high number of white Boxers being used as service dogs....
Genetically, white Boxers have no more and no less chance of problems than their colored littermates - they have the same gene pool to draw from. They are Boxers, through and through, and they have the same qualities as colored Boxers that will make them exceptional pets
As for sex - I tend to prefer the males (but don't tell my girls that!

) They are a handful as puppies and young adults, but once they've matured they are, IMO, more laid-back and loving than the females. Of course, each individual dog is different, and I know there are many laid-back and loving females. (In fact, my brood bitch is *excellent* with children and very calm, and if I'm sitting down she has to be in my lap. She doesn't seem to express the sheer joy of being with me that my boys do, though.) I always tell people to pick the puppy that they "click" with, regardless of sex or color. If you teach your puppy how to behave around children, and you teach your children how to behave around dogs, you shouldn't have any problems. (Boxers are boisterous, though, and may knock down small children accidentally! If you start training right away not to jump on people, you can probably avoid most of these mishaps.)