Canon 17-40 vs Sigma/Tamron 17-50mm

I would like to have a wide-angle lens but not sure which one. I am puzzle of which lens is best suited for me. Currently, I have a 7D and will be getting a 5dc/1dII soon. If the money is a not problem, I would get both. Since my budget does not allow me, I would think 17-40 will be better for me so that I can use on both cameras. Does anyone have the same dilemma or any ideas/recommendation?

Cheers

I wonder if you have other lenses ?

What are your needs? It's UWA vs 1-extra stop of light.
If I had other lenses for low-light, I think I would stick with 17-40L. UWA is great fun for landscape. And when you don't need the UWA you can always walk around with it on a 7D.

The Canon 17-55mm is probably a closer match (though not in price) as the Tamron / Sigma lenses are probably cropped format lenses. 17-40mm is for full frame.

BTW, I have a 24-105m lens. I want something a bit wider. Or, just get 10-22 lens? If I get 10-22, I can't use it on a FF/1d camera. decision, decision.

Why not get a used Tamron 17-50 non VC and use it until you go FF and then sell it for pretty much what you paid for it. I did that with a 28-75/2.8 and made $25 after a year so it was better than a free rental.

You could also go with the Sigma 12-24 II now which would be pretty wide on crop and much wider on FF. It's not much more than a 17-40.