When it comes to riding, not really. In fact, many times the lower step through that is often seen on a “girls” bike makes for easier riding and balance control when a child is first starting to ride. The overall differences between the two styles differ little in their functionality and ability to be ridden.
In truth, most of the time the choice between a bike designed for boys and one designed for girls is purely a social one. Some boys prefer to ride a bike made for boys because it may look cooler to them. A young girl may like the one that is specifically designed for her because it is easier to ride and looks nicer. Or the reverse could be true. So don’t worry about getting a bike that is designed for your child’s gender, and instead focus on getting one that they like and they can relate to, regardless of whom it was designed for.