Ideally you should work both. If you do length only, you'll gain. If you do girth only, you'll gain. However, what works best is working them both. Focussing on length but doing a few girth work outs will bring you better length gains than just focussing on length.
Your length looks fine to me, sure you might want to increase it, but I'd say you're penis is closer to the average in girth, than it is in length. If I were you I'd probably focus on girth while still doing length work outs. It's entirely up to you though. It is slightly easier if you gain length and then add girth as if you build your girth up, and then try and gain length, you're going to have a dick with a much larger volume, and adding length to it will be slightly harder as you have more volume.
