Those 70-300 lenses you speak of are fantastic. Currently, my two longer zooms are the Nikon 70-300 VR, and the Tamron 70-200 2.8 DI VC. For the outdoor conditions you mentioned, either lens will do the job. My Nikon 70-300 rivals the sharpness of my Tamron (and even the Nikon 70-200 2.8 - I've shot it), and it's lighter and balances just great on my camera. I've shot it on the D90 & D600, and currently on the D610 and D750, and it feels great on all. From what I have heard and seen, the Tamron 70-300 does as well. There are things that you hear about autofocus speed, micro-contrast, etc., etc., but you will not notice the difference. Thing is though, all those great things are at an aperture of F6.3 to F8. That's fine for those ball fields during the day. In a gym, not so much. That's where the 2.8 lenses take over. What those "kit" zooms do at F8, those "pro" zooms will do at F2.8 - F4. Really makes a difference when you want to stop action indoors.

So...if you really need something that will capture the indoor stuff, I would offer to go one of two routes. One, get that 70-300 or 55-250, then maybe an 85mm 1.8 for indoor shoots. 85mm is not 300mm, so you would have to move closer, but not as close as you might think. With that 1.8 aperture though, you can crank your shutter speeds up a lot more than the kit zoom. Or, simply budget for a 70-200 2.8 that will do all the indoor stuff, plus outdoor sports, wildlife, portraits (gorgeous portraits), etc. etc. Love my Tamron! Then, you can add something like the 35mm 1.8 DX for wider shots indoors or out.

Last edited by AZ Southpaw; 06/18/16.