I bought my first D-SLR a year and a half ago. Got mysef a Nikon D7000. Just like you, I love sports photography. I had the chance to shoot soccer games, boxing matches, basketball and even few weddings. I consider myself a intermediate photographer still. But without advertising my services I've been getting few contracts here and there. I love learning about photography, but I need to get into the habit of shooting more. Instead of studying about it so much. And as I experienced more shooting opportunities, I've been feeling the limitations of my gear more and more. Shooting indoor basketball has been a nightmare without the proper lens. I already own a 70-300mm f4.5-5.6, and I'm planning on getting myself a 24-700m f2.8 soon. I have the opportunity to purchase a second body. I decided to go with a full-frame. I'm hesitating between the D700 and the D3s. The price difference between these two bodies is around 1000$. I would like to go with the D3s because of the 11 fps and the ISO of 12800. But I'm not sure if it's worth the price. What would you recommend?
I believe the answer to your question about D700 vs. the D3s centers around how you will use that camera body. If it's mainly for sports, then the D3s is the better solution. Although, the D700 (which I own) is a perfectly acceptable body for sports photography particularly with the vertical grip attachment and full-sized battery. In that configuration it shoots 8 fps. It also has good low light performance up to 6400 for those indoor and night sports assignments. Don't forget about your lenses, however. Even with the D3s, the 70-300mm f/4.5-5.6 won't be sufficient for low light sports photography. You'll need to invest in at least a f/2.8 lens. Maybe you can purchase the D700, and use the saved money to purchase a f/2.8 lens you can use for sports.