Best lense for indoor sports

[PhotoMan]

Looking to see which would be the best lense to start off with for indoor sports shooting. Recently picked up a 70D and I see that I'm needing to get new lenses for the shots that I want in the lighting im in, though i had good shots until i was getting grainy pictures with my 18-55 lense indoor at 6400 (tried adjusting and balancing things just not enough light I'm guessing). I'm shooting indoor weight lifting so I'm pretty close which is why I think a prime lense like a 50mm 1.4 would be great since I need alot more light. I don't want to be stuck in a fixed position so also debating the 16-35mm 2.8 wide angle. Just seeing what options would be best or where to atleast start off

[cicopo]

You're 2 picks are very different in price. Just how often are you at the long end of your kit lens? When you are at the long end do you need to crop much?

[ebiggs1]

You just about answered your question yourself with the, "I don't want to be stuck in a fixed position ..." statement.  This eliminates a prime lens unless you are OK with buying and carrying several with you.

The Canon EF-S 17-55mm f/2.8 IS USM Lens is a good first choice.  It is a constant f2.8 unlike your lens that quickly turns into a f5.6 lens.  This is a big deal and way better. It will show you the same view.  There are several off brand lenses in this same category you can consider but why when you have a real deal Canon available?

If you want to give a prime a go, give the Canon EF 50mm f/1.8 STM Lens a look. It is pretty cheap and you won't loose much if you don't like it.  Personally, I don't!  How you post edit can make or break a prime which have become specialized lenses lately.  The newest zooms are so much better than zooms used to be, they rival and sometimes exceed primes.

I would think the EF-S 17-55mm f/2.8 IS USM Lens would be the better choice over the  EF 16-35mm f/2.8L II USM Lens for you.  Plus it is nearly twice the price! Don't get me wrong here the  EF 16-35mm f/2.8L II USM Lens is a wonderful lens and would be a fine choice especially if you intend to upgrade your DSLR to a FF in the future.

Primes or zooms you do need to post edit your shots for the best out come.  What editor do you use?

[Waddizzle]

If it is allowed, another solution would be to invest in one of Canon's RT strobes, like the 600EX-RT, which is more than powerful enough to light up subjects more than a dozen feet away.

[ScottyP]

I would definitely get the 17-55 f/2.8 over the much more expensive and more limited range 16-35.  

I would not not be too quick to dismiss the bright prime, though.  F/1.4 is two full stops faster than f/2.8.  People talk about how prints can look ok at high ISO even when the image on your monitor looks bad, but since you and everyone else will usually be seeing your images on a big computer monitor you can't ignore the fact that at ISO higher than 800, you will see image quality issues.  I personally find ISO 800 images of people's faces often look objectionable on a crop camera, more for lack of detail than for noise. Cropping the image at all makes it worse. 

If your lens is two full stops faster, you could be shooting at ISO 400 in a situation where you'd be at ISO 1600 using an f/2.8 lens. Or at ISO 800 instead of ISO 3200. Etc.  Since the primes are so affordable I can't imagine not having at least one of them.