Fkaufman3 Loc: Florida, LA ie lower Alabama

I have canon d6 and contemplating 1d mark 4, or 1ds mark 3 would I be gaining anything esp image quality ? Speed or technology?

SharpShooter Loc: NorCal

What are you trying to do? Maybe trade then both for a 7Dmkll!
The 6 is an entry level FF and not much else. The MklV is a full bore pro sports camera but 2 generations old, soon to be 3.
The 1Dmklll in my opinion is just to old unless you're on a sports budget. The 7ll is more camera but the 6 is in neither league! ;-)
SS

CHG_CANON Loc: the Windy City

A 1DIV is going to give you a lot of camera, although not the latest and greatest sensor technology as provided by the more recent 6D. Specifically, the 1DIV would offer:

Fast 10 fps Continuous Shooting with Dual DIGIC 4 Image Processors
ISO Sensitivity from 100 up to 102400
1080p Full HD Video Recording at Selectable Frame Rates
Enhanced Flash Exposure and Control
45-point autofocus
Canon's Most Rugged and Durable Professional Camera Body

A bit more 'reach' with a 1.3x sensor

jeep_daddy Loc: Prescott AZ

Your 6D is a full frame camera body. The 1DS mark 3 is full frame but older technology. Your 6D will outperform the 1DS in all regards except for durability. The 1D bodies are pro bodies designed to last. The 6D compared to the 1D mark IV is a little different. The 1DIV is not full frame. It's a 1.3x crop factor sensor but shoots at 10 fps (frames per second) The 1DIV may have a little better focusing system but the files it produces are only 16mp images versus your 6D at 20mp images.

Fkaufman3 Loc: Florida, LA ie lower Alabama

Thanks for all the input, have decided on 6d and 7d mark 2
Thanks

SharpShooter Loc: NorCal

Without knowing your intended use, it's hard to even comment. For me a 1DmklV is hands down the better camera since I shoot a lot of sports, at which the 6 is kinda useless unless it's all you have, then it will do!
Sorry, I didn't see that mklll was the "s" model. Yes, that camera is way better than a 6 and I think more mp as well.
If your even asking, I still say get rid of both and get the 7ll, and if you have the bucks, a 5dlll.
Till you respond, there's not much else to add! Sorry ;-)
SS

Nalu Loc: Southern Arizona

Great, get both and both are great cameras. But just saying, once you experience the focusing capabilities and speed of the 7DII and the benefits of the sensor on the 6D, you will be saying you want the same characteristics in one body. Watch out, you are looking at a 1DX or, hate to even think of it, it's ultimate replacement. Hate to think about the cost of that camera. Right now, sharpshooter makes a good point about the 5DIII.

SharpShooter Loc: NorCal

F, WoW, I guess our responded must have crossed!!
Looking at your decision, I just want to say that you might want to try the 7ll first, rather than get two cameras. I don't have any actual experience with the 6d but I do own the 7ll. I also have been shooting with a 5ll for about 5 years and it's very similar to the 6 in the focus dept. I'm a big proponent of FF but it has to be better, not just FF.
I shoot the equivalent of tons of portraits(Model shoots) and had also been using my 5ll for that. It's logically better for portraits but in reality, my number of just slightly soft focus shots because of re-composing and/or the focus points just not being sensitive enough was just killing me. I found the 7ll produced far more keepers because of the superior focus system. Now out of a1500 shot session I might get 3or for soft shots compared to probably 25% previously. Now my 5ll is barely a back-up. My goal is to replace both with the new 5Ds!! Good luck with your new Canons!!!! ;-)
SS

Fkaufman3 Loc: Florida, LA ie lower Alabama

Thank you everyone that responded

jeep_daddy Loc: Prescott AZ

That's a really good choice.