5D Mk IV or 1DX Mk II?

So I'm going to upgrade and move my 5D Mk III to a back-up body. The specs on the 5D Mk IV look good, but I'm wondering if there is any good reason to take the extra step to the 1DX Mk II. I do theatrical production photography and some portrait work, so low light performance is the most important thing. Another important thing is the silent shutter on the 5D is brilliant -- is the 1DX near as quiet?

Thoughts? Thanks!

For what you do, 5D.

Very best,

Why? I mean, I love the MkIII and that's probably what I'll do, but why do you say that?

$$$ and size. The 1Dx2 is overkill for you. If you don't need the frame rate I don't see why you'd want to spend that kind of money.

Thanks

Something to consider on financial POV:

Two 5D4 is more expensive than one 1DX2.

BUT, having two 5D4 means that you'll have both main & backup camera sorted.
BUT THEN, having one 1DX2 means that you have extra spare cash you can spend on something else like lenses etc.

Back to the main topic:

Considering that the OP is looking to get one to complement his backup 5D3, I'd suggest get 5D4.
5D3 & 5D4 both have fairly similar ergonomic & system. It makes more sense to get a camera that offers very similar handling to the other one.

From what I know of the original 1DX, its quiet mode is as loud as standard shooting on the 5D3. It's a loud camera times two thanks to the high frame rate.

I do doubt that Canon would somehow make a better low-light 30mp sensor over a 20MP one within the same hardware generation, with 50% more pixels I expect a suitable increase in noise - at least if viewed at 100% on a monitor. If equalized to a common print size, chances are you wouldn't be able to tell the difference.

What it comes down to is whether 14fps is worth the extra $2,500, a reduction in resolution, and lack of quiet shooting. Chances are it's not. 7fps is still very fast.