I currently have four females and three males. They are all altered.

My females hump on each other more than my males do. Of course, it's a little less "graphic" when a female does it, as opposed to a male. Humping is a show of dominance, it doesn't have anything to do with sex. So a dominant dog will hump more than a submissive one, regardless of its gender. Also, dogs hump more in a group or pack where the order is not clearly established. For example, one of my males, Keito, is clearly and completely the alpha male, the leader of the pack. The other two males would not DREAM of humping him, he would make them so very sorry. So, I only have one male humping. However, with my females, there really isn't a clear alpha female right now, since the leader of the female pack, Queenie, died a couple of weeks ago. So all four of them hump on each other, trying to figure out who is the new boss. As far as humping on legs, pillows, stuffed animals, etc., neutering a male at an early age usually, but not always, eliminates this.

Neutering will not eliminate the protrusion of the penis. It will lessen it, but it will not eliminate it. It will happen, some dogs more and some dogs less.

My personal peeve with males is urinating to mark their territory. I have one male that would NEVER mark in the house if his life depended on it. I have one that occaisionally marks, for example, if a strange dog is in the house to visit. And we sadly have one male that pretty much LIVES in a crate, because he absolutely will not stop marking. I'm talking about twenty, thirty times per day, compulsively. He is neutered, although he was several years old before he was neutered, and he was not trained well, frankly. However, it has been my experience owning a boarding kennel and grooming shop for years that some male dogs are completely obsessed with marking, and will continue to do it despite training, neutering, punishment, etc. It's not that common, but it is a HUGE problem if you happen to get that male dog. I have seen many female dogs mark at times as well, but I've never seen one obsessively and constantly do it.

As far as personality differences, I've honestly never seen any personality traits consistently different across gender lines. I have met just as many aloof females as males. Just as many playful, protective, friendly, shy, loud, quiet, calm, etc., etc., males as females.

I know for me personally, I will only own females dogs in the future, but that's just my personal preference after having had problems with males marking.