As for the original poster's question. At 10U I would say location is the most important thing for a pitcher to have. Walks kill you at that age (or any age). After that it would be speed, Again, at 10U most girls will be intimidated by anyone throwing over 45mph. Finally, spin. Not that I don't think that it's important - quite the contrary, I just don't think many girls can effectively spin it at that age. As you get older, and depending on the level of competition, the importance of those qualities may change.
Regarding average speeds, we just finished our final 12U season as a regional level A team. In our area, I would say the average speed we faced is about 48-50mph. Now, this is all anecdotal, because there is only 1 facility in our area that has radar at the fields and using PR at a few games. We actually faced a girl in an open tournament that threw 28mph! That's what happens with averages. I'm guessing the fastest pitchers we faced were about 55-57. Our pitchers lived in the 52-54 range.
Regarding average speeds, we just finished our final 12U season as a regional level A team. In our area, I would say the average speed we faced is about 48-50mph. Now, this is all anecdotal, because there is only 1 facility in our area that has radar at the fields and using PR at a few games. We actually faced a girl in an open tournament that threw 28mph! That's what happens with averages. I'm guessing the fastest pitchers we faced were about 55-57. Our pitchers lived in the 52-54 range.